C.3 $rem Variable List

The general format of the $rem input for Q-Chem text input files is simply as follows:

$rem
   rem_variable   rem_option   [comment]
   rem_variable   rem_option   [comment]
$end

This input is not case sensitive. The following sections contain the names and options of available $rem variables for users. The format for describing each $rem variable is as follows:

REM_VARIABLE

A short description of what the variable controls

TYPE:

Defines the variable as either INTEGER, LOGICAL or STRING.

DEFAULT:

Describes Q-Chem’s internal default, if any exists.

OPTIONS:

Lists options available for the user

RECOMMENDATION:

Gives a quick recommendation.

C.3.1 General

BASIS	BASIS_LIN_DEP_THRESH
EXCHANGE	CORRELATION
ECP	JOBTYPE
METHOD	PURECART

C.3.2 SCF Control

BASIS2	BASISPROJTYPE
DIIS_PRINT	DIIS_SUBSPACE_SIZE
DIRECT_SCF	INCFOCK
MAX_DIIS_CYCLES	MAX_SCF_CYCLES
PSEUDO_CANONICAL	SCF_ALGORITHM
SCF_CONVERGENCE	SCF_FINAL_PRINT
SCF_GUESS	SCF_GUESS_MIX
SCF_GUESS_PRINT	SCF_PRINT
THRESH	THRESH_DIIS_SWITCH
UNRESTRICTED	VARTHRESH

C.3.3 DFT Options

CORRELATION	EXCHANGE
FAST_XC	INC_DFT
INCDFT_DENDIFF_THRESH	INCDFT_GRIDDIFF_THRESH
INCDFT_DENDIFF_VARTHRESH	INCDFT_GRIDDIFF_VARTHRESH
XC_GRID	XC_SMART_GRID

C.3.4 Large Molecules

CFMM_ORDER	DIRECT_SCF
EPAO_ITERATE	EPAO_WEIGHTS
GRAIN	INCFOCK
INTEGRAL_2E_OPR	INTEGRALS_BUFFER
LIN_K	MEM_STATIC
MEM_TOTAL	METECO
OMEGA	PAO_ALGORITHM
PAO_METHOD	THRESH
VARTHRESH	RI_J
RI_K	ARI
ARI_R0	ARI_R1

C.3.5 Correlated Methods

AO2MO_DISK	CD_ALGORITHM
CORE_CHARACTER	CORRELATION
MEM_STATIC	MEM_TOTAL
N_FROZEN_CORE	N_FROZEN_VIRTUAL
PRINT_CORE_CHARACTER

C.3.6 Correlated Methods Handled by CCMAN and CCMAN2

Most of these $rem variables that start CC_.

These are relevant for CCSD and other CC methods (OD, VOD, CCD, QCCD, etc).

CC_CANONIZE	CC_RESTART_NO_SCF
CC_T_CONV	CC_DIIS_SIZE
CC_DIIS_FREQ	CC_DIIS_START
CC_DIIS_MAX_OVERLAP	CC_DIIS_MIN_OVERLAP
CC_RESTART	CC_SAVEAMPL

These options are only relevant to methods involving orbital optimization (OOCD, VOD, QCCD, VQCCD):

CC_MP2NO_GUESS	CC_MP2NO_GRAD
CC_DIIS	CC_DIIS12_SWITCH
CC_THETA_CONV	CC_THETA_GRAD_CONV
CC_THETA_STEPSIZE	CC_RESET_THETA
CC_THETA_GRAD_THRESH	CC_HESS_THRESH
CC_ED_CCD	CC_QCCD_THETA_SWITCH
CC_PRECONV_T2Z	CC_PRECONV_T2Z_EACH
CC_PRECONV_FZ	CC_ITERATE_OV
CC_CANONIZE_FREQ	CC_CANONIZE_FINAL

Properties and optimization:

CC_REF_PROP	CC_REF_PROP_TE
CC_FULLRESPONSE

C.3.7 Perfect pairing, Coupled cluster valence bond, and related methods

CCVB_METHOD	CCVB_GUESS
GVB_N_PAIRS	GVB_LOCAL
GVB_ORB_MAX_ITER	GVB_RESTART
GVB_ORB_CONV	GVB_ORB_SCALE
GVB_AMP_SCALE	GVB_DO_SANO
GVB_PRINT

C.3.8 Excited States: CIS, TDDFT, SF-XCIS and SOS-CIS(D)

CIS_CONVERGENCE	CIS_GUESS_DISK
CIS_GUESS_DISK_TYPE	CIS_N_ROOTS
CIS_RELAXED_DENSITY	CIS_SINGLETS
CIS_STATE_DERIV	CIS_TRIPLETS
MAX_CIS_CYCLES	RPA
XCIS	SPIN_FLIP_XCIS

C.3.9 Excited States: EOM-CC and CI Methods

Those are keywords relevant to EOM-CC and CI methods handled by CCMAN/CCMAN2. Most of these $rem variables that start CC_ and EOM_.

EOM_DAVIDSON_CONVERGENCE	EOM_DAVIDSON_MAXVECTORS
EOM_DAVIDSON_THRESHOLD	EOM_DAVIDSON_MAX_ITER
EOM_NGUESS_DOUBLES	EOM_NGUESS_SINGLES
EOM_DOEXDIAG	EOM_PRECONV_DOUBLES
EOM_PRECONV_SINGLES	EOM_PRECONV_SD
EOM_IPEA_FILTER	EOM_FAKE_IPEA
CC_REST_AMPL	CC_REST_TRIPLES
CC_EOM_PROP	CC_TRANS_PROP
CC_STATE_TO_OPT	CC_EOM_PROP
CC_EOM_PROP_TE	CC_FULLRESPONSE

C.3.10 Geometry Optimizations

CIS_STATE_DERIV	FDIFF_STEPSIZE
GEOM_OPT_COORDS	GEOM_OPT_DMAX
GEOM_OPTHESSIAN	GEOM_OPT_LINEAR_ANGLE
GEOM_OPT_MAX_CYCLES	GEOM_OPT_MAX_DIIS
GEOM_OPT_MODE	GEOM_OPT_PRINT
GEOM_OPTSYMFLAG	GEOM_OPT_PRINT
GEOM_OPTTOL_ENERGY	GEOM_OPT_TOL_DISPLACEMENT
GEOM_OPT_TOL_ENERGY	GEOM_OPT_TOL_GRADIENT
GEOMP_OPT_UPDATE	IDERIV
JOBTYPE	SCF_GUESS_ALWAYS
CC_STATE_TO_OPT

C.3.11 Vibrational Analysis

DORAMAN	CPSCF_NSEG
FDIFF_STEPSIZE	IDERIV
ISOTOPES	JOBTYPE
VIBMAN_PRINT	ANHAR
VCI	FDIFF_DER
MODE_COUPLING	IGNORE_LOW_FREQ
FDIFF_STEPSIZE_QFF

C.3.12 Reaction Coordinate Following

JOBTYPE	RPATH_COORDS
RPATH_DIRECTION	RPATH_MAX_CYCLES
RPATH_MAX_STEPSIZE	RPATH_PRINT
RPATH_TOL_DISPLACEMENT

C.3.13 NMR Calculations

D_CPSCF_PERTNUM	D_SCF_CONV_1
D_SCF_CONV_2	D_SCF_DIIS
D_SCF_MAX_1	D_SCF_MAX_2
JOBTYPE

C.3.14 Wavefunction Analysis and Molecular Properties

CHEMSOL	CHEMSOL_EFIELD
CHEMSOL_NN	CHEM_SOL_PRINT
CIS_RELAXED_DENSITY	IGDESP
INTRACULE	MULTIPOLE_ORDER
NBO	POP_MULLIKEN
PRINT_DIST_MATRIX	PRINT_ORBITALS
READ_VDW	SOLUTE_RADIUS
SOLVENT_DIELECTRIC	STABILITY_ANALYSIS
WAVEFUNCTION_ANALYSIS	WRITE_WFN

C.3.15 Symmetry

CC_SYMMETRY
SYM_IGNORE	SYMMETRY
SYMMETRY_DECOMPOSITION	SYM_TOL

C.3.16 Printing Options

CC_PRINT	CHEMSOL_PRINT
DIIS_PRINT	GEOM_OPT_PRINT
MOM_PRINT	PRINT_CORE_CHARACTER
PRINT_DIST_MATRIX	PRINT_GENERAL_BASIS
PRINT_ORBITALS	RPATH_PRINT
SCF_FINAL_PRINT	SCF_GUESS_PRINT
SCF_PRINT	VIBMAN_PRINT
WRITE_WFN

C.3.17 Resource Control

MEM_TOTAL	MEM_STATIC
AO2MO_DISK	CC_MEMORY
INTEGRALS_BUFFER	MAX_SUB_FILE_NUM
DIRECT_SCF

C.3.18 Alphabetical Listing

MBE_ORDER

Controls the truncation order $n$ for MBE.

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

$N$

Order of MBE

RECOMMENDATION:

EE-MBE and FMO can be performed up to fifth and third order, respectively.

SAPT_DISP_CORR

Request an empirical dispersion potential instead of calculating $E_{disp}^{(2)}$ and $E_{exch\text {-}disp}^{(2)}$ directly

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE

Use a dispersion force field.

FALSE

calculate $E_{disp}^{(2)}$ and $E_{exch\text {-}disp}^{(2)}$ .

RECOMMENDATION:

Using dispersion potentials reduces the scaling from ${O}(N^5)$ to ${O}(N^3)$ with respect to monomer size.

SAPT_DISP_VERSION

Controls which dispersion potential is used for SAPT

TYPE:

INTEGER

DEFAULT:

3

OPTIONS:

1

Use the “first generation” (+D1) dispersion potentials from Hesselmann [715, 693].

2

Use the “second generation” (+D2) dispersion potentials from Podeszwa. [716, 694].

3

Use the “third generation” (+D3) dispersion potentials from Lao [695].

RECOMMENDATION:

Use +D3. Whereas +D1 was fit to reproduce binding energies, the +D2 and +D3 potentials were fit directly to dispersion energies $E_{disp}^{(2)}+E_{exch\text {-}disp}^{(2)}$ computed at the SAPT(DFT) and SAPT2+(3) levels, and performs well for both total binding energies as well as individual energy components [694, 695]. In developing +D3, the training set was expanded to eliminate outliers involving $\pi$ stacking [695].

SAPT_PRINT

Controls level of printing in SAPT.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

$N$

Integer print level

RECOMMENDATION:

Larger values generate additional output.

RISAPT

Requests an RI-SAPT calculation

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE

Compute four-index integrals using the RI approximation.

FALSE

Do not use RI.

RECOMMENDATION:

Set to TRUE if an appropriate auxiliary basis set is available, as RI-SAPT is much faster and affords negligible errors (as compared to ordinary SAPT) if the auxiliary basis set is matched to the primary basis set. (The former must be specified using AUX_BASIS.)

SAPT_DSCF

Request the $\delta E_{int}^{\rm HF}$ correction

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE

Evaluate this correction.

FALSE

Omit this correction.

RECOMMENDATION:

Evaluating the $\delta E_{int}^{\rm HF}$ correction requires an SCF calculation on the entire (super)system. This corrections effectively yields a “Hartree-Fock plus dispersion” estimate of the interaction energy.

SAPT_EXCHANGE

Selects the type of first-order exchange that is used in a SAPT calculation.

TYPE:

STRING

DEFAULT:

S_SQUARED

OPTIONS:

S_SQUARED

Compute first order exchange in the single-exchange (“ $S^2$ ") approximation.

S_INVERSE

Compute the exact first order exchange.

RECOMMENDATION:

The single-exchange approximation is expected to be adequate except possibly at very short intermolecular distances, and is somewhat faster to compute.

SAPT_BASIS

Controls the MO basis used for SAPT corrections.

TYPE:

STRING

DEFAULT:

MONOMER

OPTIONS:

MONOMER

Monomer-centered basis set (MCBS).

DIMER

Dimer-centered basis set (DCBS).

PROJECTED

Projected basis set.

RECOMMENDATION:

The DCBS is more costly than the MCBS and can only be used with XPOL_MPOL_ORDER=GAS (i.e., it is not available for use with XPol). The PROJECTED choice is an efficient compromise that is available for use with XPol.

SAPT_CPHF

Requests that the second-order corrections $E_{ind}^{(2)}$ and $E_{exch\text {-}ind}^{(2)}$ be replaced by their infinite-order “response” analogues, $E_{ind,resp}^{(2)}$ and $E_{exch\text {-}ind,resp}^{(2)}$ .

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE

Evaluate the response corrections and use $E_{ind,resp}^{(2)}$ and $E_{exch\text {-}ind,resp}^{(2)}$

FALSE

Omit these corrections and use $E_{ind}^{(2)}$ and $E_{exch\text {-}ind}^{(2)}$ .

RECOMMENDATION:

Computing the response corrections requires solving CPHF equations for pair of monomers, which is somewhat expensive but may improve the accuracy when the monomers are polar.

SAPT_ORDER

Selects the order in perturbation theory for a SAPT calculation.

TYPE:

STRING

DEFAULT:

SAPT2

OPTIONS:

SAPT1

First order SAPT.

SAPT2

Second order SAPT.

ELST

First-order Rayleigh-Schrödinger perturbation theory.

RSPT

Second-order Rayleigh-Schrödinger perturbation theory.

RECOMMENDATION:

SAPT2 is the most meaningful.

MANY_BODY_BSSE

Controls the type of many-body BSSE corrections.

TYPE:

STRING

DEFAULT:

MBCP

OPTIONS:

MBCP

Use many-body counterpoise correction.

VMFC

Use Valiron-Mayer function counterpoise correction.

RECOMMENDATION:

NONE.

MBE_BSSE_ORDER

Controls the order of many-body BSSE corrections.

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

$n$

Order of many-body BSSE corrections

RECOMMENDATION:

MBCP and VMFC can be performed up to third and fourth order, respectively.

SAPT

Requests a SAPT calculation.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE

Run a SAPT calculation.

FALSE

Do not run SAPT.

RECOMMENDATION:

If SAPT is set to TRUE, one should also specify XPOL=TRUE and XPOL_MPOL_ORDER=GAS.

XPOL_MPOL_ORDER

Controls the order of multipole expansion that describes electrostatic interactions.

TYPE:

STRING

DEFAULT:

CHARGES

OPTIONS:

GAS

No electrostatic embedding; monomers are in the gas phase.

CHARGES

Charge embedding.

DENSITY

Density embedding.

RECOMMENDATION:

Should be set to GAS to do a dimer SAPT calculation (see Section 12.8).

XPOL_PRINT

Print level for XPol calculations.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

$N$

Integer print level

RECOMMENDATION:

Higher values prints more information

FEFP_EFP

Specifies that fEFP_EFP calculation is requested to compute the total interaction energies between a ligand (the last fragment in the $efp_fragments section) and the protein (represented by fEFP)

TYPE:

STRING

DEFAULT:

OFF

OPTIONS:

OFF

disables fEFP

LA

enables fEFP with the Link Atom (HLA or CLA) scheme (only electrostatics and polarization)

MFCC

enables fEFP with MFCC (only electrostatics)

RECOMMENDATION:

The keyword should be invoked if EFP/fEFP is requested (interaction energy calculations). This keyword has to be employed with EFP_FRAGMENT_ONLY = TRUE. To switch on/off electrostatics or polarzation interactions, the usual EFP controls are employed.

FEFP_QM

Specifies that fEFP_QM calculation is requested to perform a QM/fEFPcompute computation. The fEFP part is a fractionated macromolecule.

TYPE:

STRING

DEFAULT:

OFF

OPTIONS:

OFF

disables fEFP_QM and performs a QM/EFP calculation

LA

enables fEFP_QM with the Link Atom scheme

RECOMMENDATION:

The keyword should be invoked if QM/fEFP is requested. This keyword has to be employed with efp_fragment_only false. Only electrostatics is available.

XPOL_CHARGE_TYPE

Controls the type of atom-centered embedding charges for XPol calculations.

TYPE:

STRING

DEFAULT:

QLOWDIN

OPTIONS:

QLOWDIN

Löwdin charges.

QMULLIKEN

Mulliken charges.

QCHELPG

CHELPG charges.

RECOMMENDATION:

Problems with Mulliken charges in extended basis sets can lead to XPol convergence failure. Löwdin charges tend to be more stable, and CHELPG charges are both robust and provide an accurate electrostatic embedding. However, CHELPG charges are more expensive to compute, and analytic energy gradients are not yet available for this choice.

ADC_C_C

Set the spin-opposite scaling parameter $c_ c$ for the ADC(2) calculation. The parameter value is obtained by multiplying the given integer by $10^{-3}$ .

TYPE:

INTEGER

DEFAULT:

1170

Optimized value $c_ c=1.17$ for ADC(2)-s or

1000

$c_ c=1.0$ for ADC(2)-x

OPTIONS:

$n$

Corresponding to $n \cdot 10^{-3}$

RECOMMENDATION:

Use default

ADC_C_T

Set the spin-opposite scaling parameter $c_ T$ for an SOS-ADC(2) calculation. The parameter value is obtained by multiplying the given integer by $10^{-3}$ .

TYPE:

INTEGER

DEFAULT:

1300

Optimized value $c_ T = 1.3$ .

OPTIONS:

$n$

Corresponding to $n \cdot 10^{-3}$

RECOMMENDATION:

Use default

ADC_C_X

Set the spin-opposite scaling parameter $c_ x$ for the ADC(2)-x calculation. The parameter value is obtained by multiplying the given integer by $10^{-3}$ .

TYPE:

INTEGER

DEFAULT:

1300

Optimized value $c_ x = 0.9$ for ADC(2)-x.

OPTIONS:

$n$

Corresponding to $n \cdot 10^{-3}$

RECOMMENDATION:

Use default

ADC_DAVIDSON_CONV

Controls the convergence criterion of the Davidson procedure.

TYPE:

INTEGER

DEFAULT:

$6$

Corresponding to $10^{-6}$

OPTIONS:

$n \leq 12$

Corresponding to $10^{-n}$ .

RECOMMENDATION:

Use default unless higher accuracy is required or convergence problems are encountered.

ADC_DAVIDSON_MAXITER

Controls the maximum number of iterations of the Davidson procedure.

TYPE:

INTEGER

DEFAULT:

60

OPTIONS:

$n$

Number of iterations

RECOMMENDATION:

Use default unless convergence problems are encountered.

ADC_DAVIDSON_MAXSUBSPACE

Controls the maximum subspace size for the Davidson procedure.

TYPE:

INTEGER

DEFAULT:

$5 \times$ the number of excited states to be calculated.

OPTIONS:

$n$

User-defined integer.

RECOMMENDATION:

Should be at least $2-4 \times$ the number of excited states to calculate. The larger the value the more disk space is required.

ADC_DAVIDSON_THRESH

Controls the threshold for the norm of expansion vectors to be added during the Davidson procedure.

TYPE:

INTEGER

DEFAULT:

Twice the value of ADC_DAVIDSON_CONV, but at maximum $10^{-14}$ .

OPTIONS:

$n \leq 14$

Corresponding to $10^{-n}$

RECOMMENDATION:

Use default unless convergence problems are encountered. The threshold value $10^{-n}$ should always be smaller than the convergence criterion ADC_DAVIDSON_CONV.

ADC_DIIS_ECONV

Controls the convergence criterion for the excited state energy during DIIS.

TYPE:

INTEGER

DEFAULT:

6

Corresponding to $10^{-6}$

OPTIONS:

$n$

Corresponding to $10^{-n}$

RECOMMENDATION:

None

ADC_DIIS_MAXITER

Controls the maximum number of DIIS iterations.

TYPE:

INTEGER

DEFAULT:

50

OPTIONS:

$n$

User-defined integer.

RECOMMENDATION:

Increase in case of slow convergence.

ADC_DIIS_RCONV

Convergence criterion for the residual vector norm of the excited state during DIIS.

TYPE:

INTEGER

DEFAULT:

6

Corresponding to $10^{-6}$

OPTIONS:

$n$

Corresponding to $10^{-n}$

RECOMMENDATION:

None

ADC_DIIS_SIZE

Controls the size of the DIIS subspace.

TYPE:

INTEGER

DEFAULT:

7

OPTIONS:

$n$

User-defined integer

RECOMMENDATION:

None

ADC_DIIS_START

Controls the iteration step at which DIIS is turned on.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

$n$

User-defined integer.

RECOMMENDATION:

Set to a large number to switch off DIIS steps.

ADC_DO_DIIS

Activates the use of the DIIS algorithm for the calculation of ADC(2) excited states.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Use DIIS algorithm.

FALSE

Do diagonalization using Davidson algorithm.

RECOMMENDATION:

None.

ADC_NGUESS_DOUBLES

Controls the number of excited state guess vectors which are double excitations.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-defined integer.

RECOMMENDATION:

ADC_NGUESS_SINGLES

Controls the number of excited state guess vectors which are single excitations. If the number of requested excited states exceeds the total number of guess vectors (singles and doubles), this parameter is automatically adjusted, so that the number of guess vectors matches the number of requested excited states.

TYPE:

INTEGER

DEFAULT:

Equals to the number of excited states requested.

OPTIONS:

$n$

User-defined integer.

RECOMMENDATION:

ADC_PRINT

Controls the amount of printing during an ADC calculation.

TYPE:

INTEGER

DEFAULT:

1

Basic status information and results are printed.

OPTIONS:

0

Quiet: almost only results are printed.

1

Normal: basic status information and results are printed.

2

Debug1: more status information, extended information on timings.

...

RECOMMENDATION:

Use default.

ADC_PROP_ES2ES

Controls the calculation of transition properties between excited states (currently only transition dipole moments and oscillator strengths), as well as the computation of two-photon absorption cross-sections of excited states using the sum-over-states expression.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Calculate state-to-state transition properties.

FALSE

Do not compute transition properties between excited states.

RECOMMENDATION:

Set to TRUE, if state-to-state properties or sum-over-states two-photon absorption cross-sections are required.

ADC_PROP_ES

Controls the calculation of excited state properties (currently only dipole moments).

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Calculate excited state properties.

FALSE

Do not compute state properties.

RECOMMENDATION:

Set to TRUE, if properties are required.

ADC_PROP_TPA

Controls the calculation of two-photon absorption cross-sections of excited states using matrix inversion techniques.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Calculate two-photon absorption cross-sections.

FALSE

Do not compute two-photon absorption cross-sections.

RECOMMENDATION:

Set to TRUE, if to obtain two-photon absorption cross-sections.

ADD_CHARGED_CAGE

Add a point charge cage of a given radius and total charge.

TYPE:

INTEGER

DEFAULT:

0 no cage.

OPTIONS:

0 no cage.

1 dodecahedral cage.

2 spherical cage.

RECOMMENDATION:

Spherical cage is expected to yield more accurate results, especially for small radii.

AIMD_FICT_MASS

Specifies the value of the fictitious electronic mass $\mu$ , in atomic units, where $\mu$ has dimensions of (energy) $\times$ (time) $^{2}$ .

TYPE:

INTEGER

DEFAULT:

None

OPTIONS:

User-specified

RECOMMENDATION:

Values in the range of 50–200 a.u. have been employed in test calculations; consult [206] for examples and discussion.

AIMD_INIT_VELOC

Specifies the method for selecting initial nuclear velocities.

TYPE:

STRING

DEFAULT:

None

OPTIONS:

THERMAL

Random sampling of nuclear velocities from a Maxwell-Boltzmann

distribution. The user must specify the temperature in Kelvin via

the $rem variable AIMD_TEMP.

ZPE

Choose velocities in order to put zero-point vibrational energy into

each normal mode, with random signs. This option requires that a

frequency job to be run beforehand.

QUASICLASSICAL

Puts vibrational energy into each normal mode. In contrast to the

ZPE option, here the vibrational energies are sampled from a

Boltzmann distribution at the desired simulation temperature. This

also triggers several other options, as described below.

RECOMMENDATION:

This variable need only be specified in the event that velocities are not specified explicitly in a $velocity section.

AIMD_METHOD

Selects an ab initio molecular dynamics algorithm.

TYPE:

STRING

DEFAULT:

BOMD

OPTIONS:

BOMD

Born-Oppenheimer molecular dynamics.

CURVY

Curvy-steps Extended Lagrangian molecular dynamics.

RECOMMENDATION:

BOMD yields exact classical molecular dynamics, provided that the energy is tolerably conserved. ELMD is an approximation to exact classical dynamics whose validity should be tested for the properties of interest.

AIMD_MOMENTS

Requests that multipole moments be output at each time step.

TYPE:

INTEGER

DEFAULT:

0

Do not output multipole moments.

OPTIONS:

$n$

Output the first $n$ multipole moments.

RECOMMENDATION:

None

AIMD_NUCL_DACF_POINTS

Number of time points to utilize in the dipole autocorrelation function for an AIMD trajectory

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not compute dipole autocorrelation function.

$1\leq n \leq \mbox{{\small AIMD\_ STEPS}}$

Compute dipole autocorrelation function for last $n$

timesteps of the trajectory.

RECOMMENDATION:

If the DACF is desired, set equal to AIMD_STEPS.

AIMD_NUCL_SAMPLE_RATE

The rate at which sampling is performed for the velocity and/or dipole autocorrelation function(s). Specified as a multiple of steps; i.e., sampling every step is 1.

TYPE:

INTEGER

DEFAULT:

None.

OPTIONS:

$1\leq n \leq \mbox{{\small AIMD\_ STEPS}}$

Update the velocity/dipole autocorrelation function

every $n$ steps.

RECOMMENDATION:

Since the velocity and dipole moment are routinely calculated for ab initio methods, this variable should almost always be set to 1 when the VACF/DACF are desired.

AIMD_NUCL_VACF_POINTS

Number of time points to utilize in the velocity autocorrelation function for an AIMD trajectory

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not compute velocity autocorrelation function.

$1\leq n \leq \mbox{{\small AIMD\_ STEPS}}$

Compute velocity autocorrelation function for last $n$

time steps of the trajectory.

RECOMMENDATION:

If the VACF is desired, set equal to AIMD_STEPS.

AIMD_QCT_INITPOS

Chooses the initial geometry in a QCT-MD simulation.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$0$

Use the equilibrium geometry.

$n$

Picks a random geometry according to the harmonic vibrational wavefunction.

$-n$

Generates $n$ random geometries sampled from

the harmonic vibrational wavefunction.

RECOMMENDATION:

None.

AIMD_QCT_WHICH_TRAJECTORY

Picks a set of vibrational quantum numbers from a random distribution.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

$n$

Picks the $n$ th set of random initial velocities.

$-n$

Uses an average over $n$ random initial velocities.

RECOMMENDATION:

Pick a positive number if you want the initial velocities to correspond to a particular set of vibrational occupation numbers and choose a different number for each of your trajectories. If initial velocities are desired that corresponds to an average over $n$ trajectories, pick a negative number.

AIMD_STEPS

Specifies the requested number of molecular dynamics steps.

TYPE:

INTEGER

DEFAULT:

None.

OPTIONS:

User-specified.

RECOMMENDATION:

None.

AIMD_TEMP

Specifies a temperature (in Kelvin) for Maxwell-Boltzmann velocity sampling.

TYPE:

INTEGER

DEFAULT:

None

OPTIONS:

User-specified number of Kelvin.

RECOMMENDATION:

This variable is only useful in conjunction with AIMD_INIT_VELOC = THERMAL. Note that the simulations are run at constant energy, rather than constant temperature, so the mean nuclear kinetic energy will fluctuate in the course of the simulation.

ANHAR_SEL

Select a subset of normal modes for subsequent anharmonic frequency analysis.

TYPE:

LOGICAL

DEFAULT:

FALSE

Use all normal modes

OPTIONS:

TRUE

Select subset of normal modes

RECOMMENDATION:

None

ANHAR

Performing various nuclear vibrational theory (TOSH, VPT2, VCI) calculations to obtain vibrational anharmonic frequencies.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Carry out the anharmonic frequency calculation.

FALSE

Do harmonic frequency calculation.

RECOMMENDATION:

Since this calculation involves the third and fourth derivatives at the minimum of the potential energy surface, it is recommended that the GEOM_OPT_TOL_DISPLACEMENT, GEOM_OPT_TOL_GRADIENT and GEOM_OPT_TOL_ENERGY tolerances are set tighter. Note that VPT2 calculations may fail if the system involves accidental degenerate resonances. See the VCI $rem variable for more details about increasing the accuracy of anharmonic calculations.

AO2MO_DISK

Sets the scratch space size for individual program modules

TYPE:

INTEGER

DEFAULT:

2000

2 Gb

OPTIONS:

$n$

User-defined number of megabytes.

RECOMMENDATION:

The minimum disk requirement of RI-CIS(D) is approximately $3SOVXD$ . Again, the batching scheme will become more efficient with more available disk space. There is no simple formula for SOS-CIS(D) and SOS-CIS(D $_0$ ) disk requirement. However, because the disk space is abundant in modern computers, this should not pose any problem. Just put the available disk space size in this case. The actual disk usage information will also be printed in the output file.

AO2MO_DISK

Sets the amount of disk space (in megabytes) available for MP2 calculations.

TYPE:

INTEGER

DEFAULT:

2000

Corresponding to 2000 Mb.

OPTIONS:

$n$

User-defined number of megabytes.

RECOMMENDATION:

Should be set as large as possible, discussed in Section 5.3.1.

ARI_R0

Determines the value of the inner fitting radius (in ngstroms)

TYPE:

INTEGER

DEFAULT:

4

A value of 4 will be added to the atomic van der Waals radius.

OPTIONS:

$n$

User defined radius.

RECOMMENDATION:

For some systems the default value may be too small and the calculation will become unstable.

ARI_R1

Determines the value of the outer fitting radius (in ngstroms)

TYPE:

INTEGER

DEFAULT:

5

A value of 5 will be added to the atomic van der Waals radius.

OPTIONS:

$n$

User defined radius.

RECOMMENDATION:

For some systems the default value may be too small and the calculation will become unstable. This value also determines, in part, the smoothness of the potential energy surface.

ARI

Toggles the use of the atomic resolution-of-the-identity (ARI) approximation.

TYPE:

LOGICAL

DEFAULT:

FALSE

ARI will not be used by default for an RI-JK calculation.

OPTIONS:

TRUE

Turn on ARI.

RECOMMENDATION:

For large (especially 1D and 2D) molecules the approximation may yield significant improvements in Fock evaluation time.

AUX_BASIS

Specifies the type of auxiliary basis to be used in a method that involves RI-fitting procedures.

TYPE:

STRING

DEFAULT:

No default is assigned. Must be defined in the input

OPTIONS:

Symbol. Choose among the auxiliary basis sets collected in the qchem qcaux basis library

RECOMMENDATION:

Try a few different types of aux bases first

BASIS2

Sets the small basis set to use in basis set projection.

TYPE:

STRING

DEFAULT:

No second basis set default.

OPTIONS:

Symbol. Use standard basis sets as per Chapter 7.

BASIS2_GEN

General BASIS2

BASIS2_MIXED

Mixed BASIS2

RECOMMENDATION:

BASIS2 should be smaller than BASIS. There is little advantage to using a basis larger than a minimal basis when BASIS2 is used for initial guess purposes. Larger, standardized BASIS2 options are available for dual-basis calculations (see Section 4.7).

BASISPROJTYPE

Determines which method to use when projecting the density matrix of BASIS2

TYPE:

STRING

DEFAULT:

FOPPROJECTION (when DUAL_BASIS_ENERGY=false)

OVPROJECTION (when DUAL_BASIS_ENERGY=true)

OPTIONS:

FOPPROJECTION

Construct the Fock matrix in the second basis

OVPROJECTION

Projects MO’s from BASIS2 to BASIS.

RECOMMENDATION:

None

BASIS_LIN_DEP_THRESH

Sets the threshold for determining linear dependence in the basis set

TYPE:

INTEGER

DEFAULT:

6

Corresponding to a threshold of $10^{-6}$

OPTIONS:

$n$

Sets the threshold to $10^{-n}$

RECOMMENDATION:

Set to 5 or smaller if you have a poorly behaved SCF and you suspect linear dependence in you basis set. Lower values (larger thresholds) may affect the accuracy of the calculation.

BASIS

Specifies the basis sets to be used.

TYPE:

STRING

DEFAULT:

No default basis set

OPTIONS:

General, Gen

User defined ($basis keyword required).

Symbol

Use standard basis sets as per Chapter 7.

Mixed

Use a mixture of basis sets (see Chapter 7).

RECOMMENDATION:

Consult literature and reviews to aid your selection.

BOYSCALC

Specifies the Boys localized orbitals are to be calculated

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not perform localize the occupied space.

1

Allow core-valence mixing in Boys localization.

2

Localize core and valence separately.

RECOMMENDATION:

None

BOYS_CIS_NUMSTATE

Define how many states to mix with Boys localized diabatization.

TYPE:

INTEGER

DEFAULT:

0

Do not perform Boys localized diabatization.

OPTIONS:

1 to N where N is the number of CIS states requested (CIS_N_ROOTS)

RECOMMENDATION:

It is usually not wise to mix adiabatic states that are separated by more than a few eV or a typical reorganization energy in solvent.

CAGE_CHARGE

Defines the total charge of the cage.

TYPE:

INTEGER

DEFAULT:

400 Add a cage charged +4e.

OPTIONS:

n total charge of the cage is n/100 a.u.

RECOMMENDATION:

None

CAGE_POINTS

Defines number of point charges for the spherical cage.

TYPE:

INTEGER

DEFAULT:

100

OPTIONS:

n n point charges are used.

RECOMMENDATION:

None

CAGE_RADIUS

Defines radius of the charged cage.

TYPE:

INTEGER

DEFAULT:

225

OPTIONS:

n radius is n/100 .

RECOMMENDATION:

None

CCVB_GUESS

Specifies the initial guess for CCVB calculations

TYPE:

INTEGER

DEFAULT:

NONE

OPTIONS:

1

Standard GVBMAN guess (orbital localization via GVB_LOCAL + Sano procedure).

2

Use orbitals from previous GVBMAN calculation, along with SCF_GUESS = read.

3

Convert UHF orbitals into pairing VB form.

RECOMMENDATION:

Option 1 is the most useful overall. The success of GVBMAN methods is often dependent on localized orbitals, and this guess shoots for these. Option 2 is useful for comparing results to other GVBMAN methods, or if other GVBMAN methods are able to obtain a desired result more efficiently. Option 3 can be useful for bond-breaking situations when a pertinent UHF solution has been found. It works best for small systems, or if the unrestriction is a local phenomenon within a larger molecule. If the unrestriction is nonlocal and the system is large, this guess will often produce a solution that is not the global minimum. Any UHF solution has a certain number of pairs that are unrestricted, and this will be output by the program. If GVB_N_PAIRS exceeds this number, the standard GVBMAN initial-guess procedure will be used to obtain a guess for the excess pairs

CCVB_METHOD

Optionally modifies the basic CCVB method

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

1

Standard CCVB model

3

Independent electron pair approximation (IEPA) to CCVB

4

Variational PP (the CCVB reference energy)

RECOMMENDATION:

Option 1 is generally recommended. Option 4 is useful for preconditioning, and for obtaining localized-orbital solutions, which may be used in subsequent calculations. It is also useful for cases in which the regular GVBMAN PP code becomes variationally unstable. Option 3 is a simple independent-amplitude approximation to CCVB. It avoids the cubic-scaling amplitude equations of CCVB, and also is able to reach the correct dissociation energy for any molecular system (unlike regular CCVB which does so only for cases in which UHF can reach a correct dissociate limit). However the IEPA approximation to CCVB is sometimes variationally unstable, which we have yet to observe in regular CCVB.

CC_CALC_SOC

Whether or not the spin-orbit couplings between CC/EOM electronic states will be calculated. By default, the couplings are calculated between the CCSD reference and the EOM-CCSD target states. In order to calculate couplings between EOM states, CC_STATE_TO_OPT must specify the initial EOM state.

TYPE:

LOGICAL

DEFAULT:

FALSE (no spin-orbit couplings will be calculated)

OPTIONS:

FALSE, TRUE

RECOMMENDATION:

One-electron and mean-field two-electron SOCs will be computed by default. To enable full two-electron SOCs, two-particle EOM properties must be turned on (see CC_EOM_PROP_TE).

CC_CANONIZE_FINAL

Whether to semi-canonicalize orbitals at the end of the ground state calculation.

TYPE:

LOGICAL

DEFAULT:

FALSE

unless required

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

Should not normally have to be altered.

CC_CANONIZE_FREQ

The orbitals will be semi-canonicalized every $n$ theta resets. The thetas (orbital rotation angles) are reset every CC_RESET_THETA iterations. The counting of iterations differs for active space (VOD, VQCCD) calculations, where the orbitals are always canonicalized at the first theta-reset.

TYPE:

INTEGER

DEFAULT:

50

OPTIONS:

$n$

User-defined integer

RECOMMENDATION:

Smaller values can be tried in cases that do not converge.

CC_CANONIZE

Whether to semi-canonicalize orbitals at the start of the calculation (i.e. Fock matrix is diagonalized in each orbital subspace)

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

Should not normally have to be altered.

CC_CONVERGENCE

Overall convergence criterion for the coupled-cluster codes. This is designed to ensure at least $n$ significant digits in the calculated energy, and automatically sets the other convergence-related variables (CC_E_CONV, CC_T_CONV, CC_THETA_CONV, CC_THETA_GRAD_CONV) [ $10^{-n}$ ].

TYPE:

INTEGER

DEFAULT:

6

Energies.

7

Gradients.

OPTIONS:

$n$

Corresponding to $10^{-n}$ convergence criterion. Amplitude convergence is set

automatically to match energy convergence.

RECOMMENDATION:

Use default

CC_DIIS12_SWITCH

When to switch from DIIS2 to DIIS1 procedure, or when DIIS2 procedure is required to generate DIIS guesses less frequently. Total value of DIIS error vector must be less than $10^{-n}$ , where $n$ is the value of this option.

TYPE:

INTEGER

DEFAULT:

5

OPTIONS:

$n$

User-defined integer

RECOMMENDATION:

None

CC_DIIS_FREQ

DIIS extrapolation will be attempted every n iterations. However, DIIS2 will be attempted every iteration while total error vector exceeds CC_DIIS12_SWITCH. DIIS1 cannot generate guesses more frequently than every 2 iterations.

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

$N$

User-defined integer

RECOMMENDATION:

None

CC_DIIS_MAX_OVERLAP

DIIS extrapolations will not begin until square root of the maximum element of the error overlap matrix drops below this value.

TYPE:

DOUBLE

DEFAULT:

100

Corresponding to 1.0

OPTIONS:

$abcde$

Integer code is mapped to $abc\times 10^{-de}$

RECOMMENDATION:

None

CC_DIIS_MIN_OVERLAP

The DIIS procedure will be halted when the square root of smallest element of the error overlap matrix is less than $10^{-n}$ , where $n$ is the value of this option. Small values of the B matrix mean it will become near-singular, making the DIIS equations difficult to solve.

TYPE:

INTEGER

DEFAULT:

11

OPTIONS:

$n$

User-defined integer

RECOMMENDATION:

None

CC_DIIS_SIZE

Specifies the maximum size of the DIIS space.

TYPE:

INTEGER

DEFAULT:

7

OPTIONS:

$n$

User-defined integer

RECOMMENDATION:

Larger values involve larger amounts of disk storage.

CC_DIIS_START

Iteration number when DIIS is turned on. Set to a large number to disable DIIS.

TYPE:

INTEGER

DEFAULT:

3

OPTIONS:

$n$

User-defined

RECOMMENDATION:

Occasionally DIIS can cause optimized orbital coupled-cluster calculations to diverge through large orbital changes. If this is seen, DIIS should be disabled.

CC_DIIS

Specify the version of Pulay’s Direct Inversion of the Iterative Subspace (DIIS) convergence accelerator to be used in the coupled-cluster code.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Activates procedure 2 initially, and procedure 1 when gradients are smaller

than DIIS12_SWITCH.

1

Uses error vectors defined as differences between parameter vectors from

successive iterations. Most efficient near convergence.

2

Error vectors are defined as gradients scaled by square root of the

approximate diagonal Hessian. Most efficient far from convergence.

RECOMMENDATION:

DIIS1 can be more stable. If DIIS problems are encountered in the early stages of a calculation (when gradients are large) try DIIS1.

CC_DOV_THRESH

Specifies the minimum allowed values for the coupled-cluster energy denominators. Smaller values are replaced by this constant during early iterations only, so the final results are unaffected, but initial convergence is improved when the guess is poor.

TYPE:

DOUBLE

DEFAULT:

2502

Corresponding to 0.25

OPTIONS:

$abcde$

Integer code is mapped to $abc\times 10^{-de}$

RECOMMENDATION:

Increase to 0.5 or 0.75 for non-convergent coupled-cluster calculations.

CC_DOV_THRESH

Specifies minimum allowed values for the coupled-cluster energy denominators. Smaller values are replaced by this constant during early iterations only, so the final results are unaffected, but initial convergence is improved when the HOMO-LUMO gap is small or when non-conventional references are used.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$abcde$

Integer code is mapped to $abc\times 10^{-de}$ , e.g., $2502$ corresponds to 0.25

RECOMMENDATION:

Increase to 0.25, 0.5 or 0.75 for non convergent coupled-cluster calculations.

CC_DO_DYSON_EE

Whether excited state Dyson orbitals will be calculated for EOM-IP/EA-CCSD calculations.

TYPE:

LOGICAL

DEFAULT:

FALSE (the option must be specified to run this calculation)

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

none

CC_DO_DYSON

Whether ground state Dyson orbitals will be calculated for EOM-IP/EA-CCSD calculations.

TYPE:

LOGICAL

DEFAULT:

FALSE (the option must be specified to run this calculation)

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

none

CC_EOM_2PA

Whether or not the transition moments and cross sections for two-photon absorption will be calculated. By default, the transition moments are calculated between the CCSD reference and the EOM-CCSD target states. In order to calculate transition moments between a set of EOM-CCSD states and another EOM-CCSD state, the CC_STATE_TO_OPT must be specified for this state.

TYPE:

INTEGER

DEFAULT:

0 (do not compute 2PA transition moments)

OPTIONS:

1

Compute 2PA using the fastest algorithm (use $\tilde{\sigma }$ -intermediates for canonical

and $\sigma$ -intermediates for RI/CD response calculations).

2

Use $\sigma$ -intermediates for 2PA response equation calculations.

3

Use $\tilde{\sigma }$ -intermediates for 2PA response equation calculations.

RECOMMENDATION:

Additional response equations (6 for each target state) will be solved, which increases the cost of calculations. The cost of 2PA moments is about 10 times that of energy calculation. Use default algorithm. Setting CC_EOM_2PA $>$ 0 turns on CC_TRANS_PROP.

CC_EOM_PROP

Whether or not the non-relaxed (expectation value) one-particle EOM-CCSD target state properties will be calculated. The properties currently include permanent dipole moment, the second moments $\ensuremath{\langle }X^2\ensuremath{\rangle }$ , $\ensuremath{\langle }Y^2\ensuremath{\rangle }$ , and $\ensuremath{\langle }Z^2\ensuremath{\rangle }$ of electron density, and the total $\ensuremath{\langle }R^2\ensuremath{\rangle }= \ensuremath{\langle }X^2\ensuremath{\rangle }+\ensuremath{\langle }Y^2\ensuremath{\rangle }+\ensuremath{\langle }Z^2\ensuremath{\rangle }$ (in atomic units). Incompatible with JOBTYPE=FORCE, OPT, FREQ.

TYPE:

LOGICAL

DEFAULT:

FALSE (no one-particle properties will be calculated)

OPTIONS:

FALSE, TRUE

RECOMMENDATION:

Additional equations (EOM-CCSD equations for the left eigenvectors) need to be solved for properties, approximately doubling the cost of calculation for each irrep. Sometimes the equations for left and right eigenvectors converge to different sets of target states. In this case, the simultaneous iterations of left and right vectors will diverge, and the properties for several or all the target states may be incorrect! The problem can be solved by varying the number of requested states, specified with XX_STATES, or the number of guess vectors (EOM_NGUESS_SINGLES). The cost of the one-particle properties calculation itself is low. The one-particle density of an EOM-CCSD target state can be analyzed with NBO package by specifying the state with CC_STATE_TO_OPT and requesting NBO=TRUE and CC_EOM_PROP=TRUE.

CC_E_CONV

Convergence desired on the change in total energy, between iterations.

TYPE:

INTEGER

DEFAULT:

10

OPTIONS:

$n$

$10^{-n}$ convergence criterion.

RECOMMENDATION:

None

CC_FNO_THRESH

Initialize the FNO truncation and sets the threshold to be used for both cutoffs (OCCT and POVO)

TYPE:

INTEGER

DEFAULT:

None

OPTIONS:

range

0000-10000

$abcd$

Corresponding to $ab.cd$ %

RECOMMENDATION:

None

CC_FNO_USEPOP

Selection of the truncation scheme

TYPE:

INTEGER

DEFAULT:

1

OCCT

OPTIONS:

0

POVO

RECOMMENDATION:

None

CC_FULLRESPONSE

Fully relaxed properties (including orbital relaxation terms) will be computed. The variable CC_EOM_PROP must be also set to TRUE.

TYPE:

LOGICAL

DEFAULT:

FALSE

(no orbital response will be calculated)

OPTIONS:

FALSE, TRUE

RECOMMENDATION:

Not available for non-UHF/RHF references. Only available for EOM/CI methods for which analytic gradients are available.

CC_FULLRESPONSE

Fully relaxed properties (including orbital relaxation terms) will be computed. The variable CC_REF_PROP must be also set to TRUE.

TYPE:

LOGICAL

DEFAULT:

FALSE

(no orbital response will be calculated)

OPTIONS:

FALSE, TRUE

RECOMMENDATION:

Not available for non UHF/RHF references and for the methods that do not have analytic gradients (e.g., QCISD).

CC_HESS_THRESH

Minimum allowed value for the orbital Hessian. Smaller values are replaced by this constant.

TYPE:

DOUBLE

DEFAULT:

102

Corresponding to 0.01

OPTIONS:

$abcde$

Integer code is mapped to $abc\times 10^{-de}$

RECOMMENDATION:

None

CC_INCL_CORE_CORR

Whether to include the correlation contribution from frozen core orbitals in non iterative (2) corrections, such as OD(2) and CCSD(2).

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

Use default unless no core-valence or core correlation is desired (e.g., for comparison with other methods or because the basis used cannot describe core correlation).

CC_ITERATE_ON

In active space calculations, use a “mixed” iteration procedure if the value is greater than 0. Then if the RMS orbital gradient is larger than the value of CC_THETA_GRAD_THRESH, micro-iterations will be performed to converge the occupied-virtual mixing angles for the current active space. The maximum number of space iterations is given by this option.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

Up to $n$ occupied-virtual iterations per overall cycle

RECOMMENDATION:

Can be useful for non-convergent active space calculations

CC_ITERATE_OV

In active space calculations, use a “mixed” iteration procedure if the value is greater than 0. Then, if the RMS orbital gradient is larger than the value of CC_THETA_GRAD_THRESH, micro-iterations will be performed to converge the occupied-virtual mixing angles for the current active space. The maximum number of such iterations is given by this option.

TYPE:

INTEGER

DEFAULT:

0

No “mixed” iterations

OPTIONS:

$n$

Up to $n$ occupied-virtual iterations per overall cycle

RECOMMENDATION:

Can be useful for non-convergent active space calculations.

CC_MAX_ITER

Maximum number of iterations to optimize the coupled-cluster energy.

TYPE:

INTEGER

DEFAULT:

200

OPTIONS:

$n$

up to $n$ iterations to achieve convergence.

RECOMMENDATION:

None

CC_MEMORY

Specifies the maximum size, in Mb, of the buffers for in-core storage of block-tensors in CCMAN and CCMAN2.

TYPE:

INTEGER

DEFAULT:

50% of MEM_TOTAL. If MEM_TOTAL is not set, use 1.5 Gb. A minimum of

192 Mb is hard-coded.

OPTIONS:

$n$

Integer number of Mb

RECOMMENDATION:

Larger values can give better I/O performance and are recommended for systems with large memory (add to your .qchemrc file. When running CCMAN2 exclusively on a node, CC_MEMORY should be set to 75–80% of the total available RAM. )

CC_MP2NO_GRAD

If CC_MP2NO_GUESS is TRUE, what kind of one-particle density matrix is used to make the guess orbitals?

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

1 PDM from MP2 gradient theory.

FALSE

1 PDM expanded to 2 $^{\ensuremath{\mathrm{nd}}}$ order in perturbation theory.

RECOMMENDATION:

The two definitions give generally similar performance.

CC_MP2NO_GUESS

Will guess orbitals be natural orbitals of the MP2 wavefunction? Alternatively, it is possible to use an effective one-particle density matrix to define the natural orbitals.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Use natural orbitals from an MP2 one-particle density matrix (see CC_MP2NO_GRAD).

FALSE

Use current molecular orbitals from SCF.

RECOMMENDATION:

None

CC_ORBS_PER_BLOCK

Specifies target (and maximum) size of blocks in orbital space.

TYPE:

INTEGER

DEFAULT:

16

OPTIONS:

$n$

Orbital block size of $n$ orbitals.

RECOMMENDATION:

None

CC_PRECONV_FZ

In active space methods, whether to pre-converge other wavefunction variables for fixed initial guess of active space.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

No pre-iterations before active space optimization begins.

$n$

Maximum number of pre-iterations via this procedure.

RECOMMENDATION:

None

CC_PRECONV_T2Z_EACH

Whether to pre-converge the cluster amplitudes before each change of the orbitals in optimized orbital coupled-cluster methods. The maximum number of iterations in this pre-convergence procedure is given by the value of this parameter.

TYPE:

INTEGER

DEFAULT:

0

(FALSE)

OPTIONS:

0

No pre-convergence before orbital optimization.

$n$

Up to $n$ iterations in this pre-convergence procedure.

RECOMMENDATION:

A very slow last resort option for jobs that do not converge.

CC_PRECONV_T2Z

Whether to pre-converge the cluster amplitudes before beginning orbital optimization in optimized orbital cluster methods.

TYPE:

INTEGER

DEFAULT:

0

(FALSE)

10

If CC_RESTART, CC_RESTART_NO_SCF or CC_MP2NO_GUESS are TRUE

OPTIONS:

0

No pre-convergence before orbital optimization.

$n$

Up to $n$ iterations in this pre-convergence procedure.

RECOMMENDATION:

Experiment with this option in cases of convergence failure.

CC_PRINT

Controls the output from post-MP2 coupled-cluster module of Q-Chem

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

$0\to 7$

higher values can lead to deforestation…

RECOMMENDATION:

Increase if you need more output and don’t like trees

CC_QCCD_THETA_SWITCH

QCCD calculations switch from OD to QCCD when the rotation gradient is below this threshold [ $10^{-n}$ ]

TYPE:

INTEGER

DEFAULT:

2

$10^{-2}$ switchover

OPTIONS:

$n$

$10^{-n}$ switchover

RECOMMENDATION:

None

CC_REF_PROP_TE

Request for calculation of non-relaxed two-particle CCSD properties. The two-particle properties currently include $\ensuremath{\langle }S^2\ensuremath{\rangle }$ . The one-particle properties also will be calculated, since the additional cost of the one-particle properties calculation is inferior compared to the cost of $\ensuremath{\langle }S^2\ensuremath{\rangle }$ . The variable CC_REF_PROP must be also set to TRUE.

TYPE:

LOGICAL

DEFAULT:

FALSE

(no two-particle properties will be calculated)

OPTIONS:

FALSE, TRUE

RECOMMENDATION:

The two-particle properties are computationally expensive, since they require calculation and use of the two-particle density matrix (the cost is approximately the same as the cost of an analytic gradient calculation). Do not request the two-particle properties unless you really need them.

CC_REF_PROP

Whether or not the non-relaxed (expectation value) or full response (including orbital relaxation terms) one-particle CCSD properties will be calculated. The properties currently include permanent dipole moment, the second moments $\ensuremath{\langle }X^2\ensuremath{\rangle }$ , $\ensuremath{\langle }Y^2\ensuremath{\rangle }$ , and $\ensuremath{\langle }Z^2\ensuremath{\rangle }$ of electron density, and the total $\ensuremath{\langle }R^2\ensuremath{\rangle }= \ensuremath{\langle }X^2\ensuremath{\rangle }+\ensuremath{\langle }Y^2\ensuremath{\rangle }+\ensuremath{\langle }Z^2\ensuremath{\rangle }$ (in atomic units). Incompatible with JOBTYPE=FORCE, OPT, FREQ.

TYPE:

LOGICAL

DEFAULT:

FALSE

(no one-particle properties will be calculated)

OPTIONS:

FALSE, TRUE

RECOMMENDATION:

Additional equations need to be solved (lambda CCSD equations) for properties with the cost approximately the same as CCSD equations. Use default if you do not need properties. The cost of the properties calculation itself is low. The CCSD one-particle density can be analyzed with NBO package by specifying NBO=TRUE, CC_REF_PROP=TRUE and JOBTYPE=FORCE.

CC_RESET_THETA

The reference MO coefficient matrix is reset every n iterations to help overcome problems associated with the theta metric as theta becomes large.

TYPE:

INTEGER

DEFAULT:

15

OPTIONS:

$n$

$n$ iterations between resetting orbital rotations to zero.

RECOMMENDATION:

None

CC_RESTART_NO_SCF

Should an optimized orbital coupled cluster calculation begin with optimized orbitals from a previous calculation? When TRUE, molecular orbitals are initially orthogonalized, and CC_PRECONV_T2Z and CC_CANONIZE are set to TRUE while other guess options are set to FALSE

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

None

CC_RESTART

Allows an optimized orbital coupled cluster calculation to begin with an initial guess for the orbital transformation matrix U other than the unit vector. The scratch file from a previous run must be available for the U matrix to be read successfully.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Use unit initial guess.

TRUE

Activates CC_PRECONV_T2Z, CC_CANONIZE, and

turns off CC_MP2NO_GUESS

RECOMMENDATION:

Useful for restarting a job that did not converge, if files were saved.

CC_RESTR_AMPL

Controls the restriction on amplitudes is there are restricted orbitals

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

0

All amplitudes are in the full space

1

Amplitudes are restricted, if there are restricted orbitals

RECOMMENDATION:

None

CC_RESTR_TRIPLES

Controls which space the triples correction is computed in

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Triples are computed in the full space

1

Triples are restricted to the active space

RECOMMENDATION:

None

CC_REST_AMPL

Forces the integrals, $T$ , and $R$ amplitudes to be determined in the full space even though the CC_REST_OCC and CC_REST_VIR keywords are used.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

0

Do apply restrictions

1

Do not apply restrictions

RECOMMENDATION:

None

CC_REST_OCC

Sets the number of restricted occupied orbitals including frozen occupied orbitals.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

Restrict $n$ occupied orbitals.

RECOMMENDATION:

None

CC_REST_TRIPLES

Restricts $R_3$ amplitudes to the active space, i.e., one electron should be removed from the active occupied orbital and one electron should be added to the active virtual orbital.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

1

Applies the restrictions

RECOMMENDATION:

None

CC_REST_VIR

Sets the number of restricted virtual orbitals including frozen virtual orbitals.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

Restrict $n$ virtual orbitals.

RECOMMENDATION:

None

CC_SCALE_AMP

If not 0, scales down the step for updating coupled-cluster amplitudes in cases of problematic convergence.

TYPE:

INTEGER

DEFAULT:

0

no scaling

OPTIONS:

$abcd$

Integer code is mapped to $abcd\times 10^{-2}$ , e.g., $90$ corresponds to 0.9

RECOMMENDATION:

Use 0.9 or 0.8 for non convergent coupled-cluster calculations.

CC_STATE_TO_OPT

Specifies which state to optimize.

TYPE:

INTEGER ARRAY

DEFAULT:

None

OPTIONS:

[ $i$ , $j$ ]

optimize the $j$ th state of the $i$ th irrep.

RECOMMENDATION:

None

CC_SYMMETRY

Controls the use of symmetry in coupled-cluster calculations

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

Use the point group symmetry of the molecule

FALSE

Do not use point group symmetry (all states will be of $A$ symmetry).

RECOMMENDATION:

It is automatically turned off for any finite difference calculations, e.g. second derivatives.

CC_THETA_CONV

Convergence criterion on the RMS difference between successive sets of orbital rotation angles [ $10^{-n}$ ].

TYPE:

INTEGER

DEFAULT:

5

Energies

6

Gradients

OPTIONS:

$n$

$10^{-n}$ convergence criterion.

RECOMMENDATION:

Use default

CC_THETA_GRAD_CONV

Convergence desired on the RMS gradient of the energy with respect to orbital rotation angles [ $10^{-n}$ ].

TYPE:

INTEGER

DEFAULT:

7

Energies

8

Gradients

OPTIONS:

$n$

$10^{-n}$ convergence criterion.

RECOMMENDATION:

Use default

CC_THETA_GRAD_THRESH

RMS orbital gradient threshold [ $10^{-n}$ ] above which “mixed iterations” are performed in active space calculations if CC_ITERATE_OV is TRUE.

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

$n$

$10^{-n}$ threshold.

RECOMMENDATION:

Can be made smaller if convergence difficulties are encountered.

CC_THETA_STEPSIZE

Scale factor for the orbital rotation step size. The optimal rotation steps should be approximately equal to the gradient vector.

TYPE:

INTEGER

DEFAULT:

$100$

Corresponding to 1.0

OPTIONS:

$abcde$

Integer code is mapped to $abc\times 10^{-de}$

If the initial step is smaller than 0.5, the program will increase step

when gradients are smaller than the value of THETA_GRAD_THRESH,

up to a limit of 0.5.

RECOMMENDATION:

Try a smaller value in cases of poor convergence and very large orbital gradients. For example, a value of 01001 translates to 0.1

CC_TRANS_PROP

Whether or not the transition dipole moment (in atomic units) and oscillator strength for the EOM-CCSD target states will be calculated. By default, the transition dipole moment is calculated between the CCSD reference and the EOM-CCSD target states. In order to calculate transition dipole moment between a set of EOM-CCSD states and another EOM-CCSD state, the CC_STATE_TO_OPT must be specified for this state.

TYPE:

LOGICAL

DEFAULT:

FALSE (no transition dipole and oscillator strength will be calculated)

OPTIONS:

FALSE, TRUE

RECOMMENDATION:

Additional equations (for the left EOM-CCSD eigenvectors plus lambda CCSD equations in case if transition properties between the CCSD reference and EOM-CCSD target states are requested) need to be solved for transition properties, approximately doubling the computational cost. The cost of the transition properties calculation itself is low.

CC_T_CONV

Convergence criterion on the RMS difference between successive sets of coupled-cluster doubles amplitudes [ $10^{-n}$ ]

TYPE:

INTEGER

DEFAULT:

8

energies

10

gradients

OPTIONS:

$n$

$10^{-n}$ convergence criterion.

RECOMMENDATION:

Use default

CC_Z_CONV

Convergence criterion on the RMS difference between successive doubles $Z$ -vector amplitudes [ $10^{-n}$ ].

TYPE:

INTEGER

DEFAULT:

8

Energies

10

Gradients

OPTIONS:

$n$

$10^{-n}$ convergence criterion.

RECOMMENDATION:

Use Default

CDFTCI_PRINT

Controls level of output from CDFT-CI procedure to Q-Chem output file.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Only print energies and coefficients of CDFT-CI final states

1

Level 0 plus CDFT-CI overlap, Hamiltonian, and population matrices

2

Level 1 plus eigenvectors and eigenvalues of the CDFT-CI population matrix

3

Level 2 plus promolecule orbital coefficients and energies

RECOMMENDATION:

Level 3 is primarily for program debugging; levels 1 and 2 may be useful for analyzing the coupling elements

CDFTCI_RESTART

To be used in conjunction with CDFTCI_STOP, this variable causes CDFT-CI to read already-converged states from disk and begin SCF convergence on later states. Note that the same $cdft section must be used for the stopped calculation and the restarted calculation.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

start calculations on state $n+1$

RECOMMENDATION:

Use this setting in conjunction with CDFTCI_STOP.

CDFTCI_SKIP_PROMOLECULES

Skips promolecule calculations and allows fractional charge and spin constraints to be specified directly.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

FALSE

Standard CDFT-CI calculation is performed.

TRUE

Use the given charge/spin constraints directly, with no promolecule calculations.

RECOMMENDATION:

Setting to TRUE can be useful for scanning over constraint values.

CDFTCI_STOP

The CDFT-CI procedure involves performing independent SCF calculations on distinct constrained states. It sometimes occurs that the same convergence parameters are not successful for all of the states of interest, so that a CDFT-CI calculation might converge one of these diabatic states but not the next. This variable allows a user to stop a CDFT-CI calculation after a certain number of states have been converged, with the ability to restart later on the next state, with different convergence options.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

stop after converging state $n$ (the first state is state $1$ )

$0$

do not stop early

RECOMMENDATION:

Use this setting if some diabatic states converge but others do not.

CDFTCI_SVD_THRESH

By default, a symmetric orthogonalization is performed on the CDFT-CI matrix before diagonalization. If the CDFT-CI overlap matrix is nearly singular (i.e., some of the diabatic states are nearly degenerate), then this orthogonalization can lead to numerical instability. When computing $\vec{S}^{-1/2}$ , eigenvalues smaller than $10^{-\mathrm{CDFTCI\_ SVD\_ THRESH}}$ are discarded.

TYPE:

INTEGER

DEFAULT:

4

OPTIONS:

$n$

for a threshold of $10^{-n}$ .

RECOMMENDATION:

Can be decreased if numerical instabilities are encountered in the final diagonalization.

CDFTCI

Initiates a constrained DFT-configuration interaction calculation

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Perform a CDFT-CI Calculation

FALSE

No CDFT-CI

RECOMMENDATION:

Set to TRUE if a CDFT-CI calculation is desired.

CDFT_BECKE_POP

Whether the calculation should print the Becke atomic charges at convergence

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

Print Populations

FALSE

Do not print them

RECOMMENDATION:

Use default. Note that the Mulliken populations printed at the end of an SCF run will not typically add up to the prescribed constraint value. Only the Becke populations are guaranteed to satisfy the user-specified constraints.

CDFT_CRASHONFAIL

Whether the calculation should crash or not if the constraint iterations do not converge.

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

Crash if constraint iterations do not converge.

FALSE

Do not crash.

RECOMMENDATION:

Use default.

CDFT_LAMBDA_MODE

Allows CDFT potentials to be specified directly, instead of being determined as Lagrange multipliers.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

FALSE

Standard CDFT calculations are used.

TRUE

Instead of specifying target charge and spin constraints, use the values

from the input deck as the value of the Becke weight potential

RECOMMENDATION:

Should usually be set to FALSE. Setting to TRUE can be useful to scan over different strengths of charge or spin localization, as convergence properties are improved compared to regular CDFT(-CI) calculations.

CDFT_POSTDIIS

Controls whether the constraint is enforced after DIIS extrapolation.

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

Enforce constraint after DIIS

FALSE

Do not enforce constraint after DIIS

RECOMMENDATION:

Use default unless convergence problems arise, in which case it may be beneficial to experiment with setting CDFT_POSTDIIS to FALSE. With this option set to TRUE, energies should be variational after the first iteration.

CDFT_PREDIIS

Controls whether the constraint is enforced before DIIS extrapolation.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Enforce constraint before DIIS

FALSE

Do not enforce constraint before DIIS

RECOMMENDATION:

Use default unless convergence problems arise, in which case it may be beneficial to experiment with setting CDFT_PREDIIS to TRUE. Note that it is possible to enforce the constraint both before and after DIIS by setting both CDFT_PREDIIS and CDFT_POSTDIIS to TRUE.

CDFT_THRESH

Threshold that determines how tightly the constraint must be satisfied.

TYPE:

INTEGER

DEFAULT:

5

OPTIONS:

N

Constraint is satisfied to within $10^{-N}$ .

RECOMMENDATION:

Use default unless problems occur.

CDFT

Initiates a constrained DFT calculation

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Perform a Constrained DFT Calculation

FALSE

No Density Constraint

RECOMMENDATION:

Set to TRUE if a Constrained DFT calculation is desired.

CD_ALGORITHM

Determines the algorithm for MP2 integral transformations.

TYPE:

STRING

DEFAULT:

Program determined.

OPTIONS:

DIRECT

Uses fully direct algorithm (energies only).

SEMI_DIRECT

Uses disk-based semi-direct algorithm.

LOCAL_OCCUPIED

Alternative energy algorithm (see 5.3.1).

RECOMMENDATION:

Semi-direct is usually most efficient, and will normally be chosen by default.

CFMM_ORDER

Controls the order of the multipole expansions in CFMM calculation.

TYPE:

INTEGER

DEFAULT:

15

For single point SCF accuracy

25

For tighter convergence (optimizations)

OPTIONS:

$n$

Use multipole expansions of order $n$

RECOMMENDATION:

Use default.

CHARGE_CHARGE_REPULSION

The repulsive Coulomb interaction parameter for YinYang atoms.

TYPE:

INTEGER

DEFAULT:

550

OPTIONS:

$n$

Use Q = $n \times 10^{-3}$

RECOMMENDATION:

The repulsive Coulomb potential maintains bond lengths involving YinYang atoms with the potential $V(r) = Q/r$ . The default is parameterized for carbon atoms.

CHELPG_DX

Sets the rectangular grid spacing for the traditional Cartesian CHELPG grid or the spacing between concentric Lebedev shells (when the variables CHELPG_HA and CHELPG_H are specified as well).

TYPE:

INTEGER

DEFAULT:

6

OPTIONS:

$N$

Corresponding to a grid space of $N/20$ , in .

RECOMMENDATION:

Use the default (which corresponds to the “dense grid” of Breneman and Wiberg [455]), unless the cost is prohibitive, in which case a larger value can be selected. Note that this default value is set with the Cartesian grid in mind and not the Lebedev grid. In the Lebedev case, a larger value can typically be used.

CHELPG_HA

Sets the Lebedev grid to use for non-hydrogen atoms.

TYPE:

INTEGER

DEFAULT:

NONE

OPTIONS:

$N$

Corresponding to a number of points in a Lebedev grid (see Section 4.3.14.

RECOMMENDATION:

None.

CHELPG_HEAD

Sets the “head space” [455] (radial extent) of the CHELPG grid.

TYPE:

INTEGER

DEFAULT:

30

OPTIONS:

$N$

Corresponding to a head space of $N/10$ , in .

RECOMMENDATION:

Use the default, which is the value recommended by Breneman and Wiberg [455].

CHELPG_H

Sets the Lebedev grid to use for hydrogen atoms.

TYPE:

INTEGER

DEFAULT:

NONE

OPTIONS:

$N$

Corresponding to a number of points in a Lebedev grid.

RECOMMENDATION:

CHELPG_H must always be less than or equal to CHELPG_HA. If it is greater, it will automatically be set to the value of CHELPG_HA.

CHELPG

Controls the calculation of CHELPG charges.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not calculate CHELPG charges.

TRUE

Compute CHELPG charges.

RECOMMENDATION:

Set to TRUE if desired. For large molecules, there is some overhead associated with computing CHELPG charges, especially if the number of grid points is large.

CHOLESKY_TOL

Tolerance of Cholesky decomposition of two-electron integrals

TYPE:

INTEGER

DEFAULT:

3

OPTIONS:

$n$ to define tolerance of $10^{-n}$

RECOMMENDATION:

2 - qualitative calculations, 3 - appropriate for most cases, 4 - quantitative (error in total energy typically less than 1e-6 hartree)

CISTR_PRINT

Controls level of output

TYPE:

LOGICAL

DEFAULT:

FALSE

Minimal output

OPTIONS:

TRUE

Increase output level

RECOMMENDATION:

None

CIS_AMPL_ANAL

Perform additional analysis of CIS and TDDFT excitation amplitudes, including generation of natural transition orbitals, excited-state multipole moments, and Mulliken analysis of the excited state densities and particle/hole density matrices.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Perform additional amplitude analysis.

FALSE

Do not perform additional analysis.

RECOMMENDATION:

None

CIS_CONVERGENCE

CIS is considered converged when error is less than $10^{-\ensuremath{\mathrm{CIS\_ CONVERGENCE}}}$

TYPE:

INTEGER

DEFAULT:

6

CIS convergence threshold 10 $^{-6}$

OPTIONS:

$n$

Corresponding to $10^{-n}$

RECOMMENDATION:

None

CIS_DER_COUPLE

Determines whether we are calculating nonadiabatic couplings.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Calculate nonadiabatic couplings.

FALSE

Don’t calculate nonadiabatic couplings.

RECOMMENDATION:

None.

CIS_DER_NUMSTATE

Determines among how many states we calculate nonadiabatic couplings.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Don’t calculate nonadiabatic couplings.

$n$

Calculate $n(n-1)/2$ pairs of nonadiabatic couplings.

RECOMMENDATION:

None.

CIS_DIABATH_DECOMPOSE

Decide whether or not to decompose the diabatic coupling into Coulomb, exchange, and one-electron terms.

TYPE:

LOGICAL

DEFAULT:

FALSE

Do not decompose the diabatic coupling.

OPTIONS:

TRUE

RECOMMENDATION:

These decompositions are most meaningful for electronic excitation transfer processes. Currently, available only for CIS, not for TD-DFT diabatic states.

CIS_DYNAMIC_MEM

Controls whether to use static or dynamic memory in CIS and TDDFT calculations.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Partly use static memory

TRUE

Fully use dynamic memory

RECOMMENDATION:

The default control requires static memory (MEM_STATIC) to hold a temporary array whose minimum size is $OV \times \mbox{{\small CIS\_ N\_ ROOTS}}$ . For a large calculation, one has to specify a large value for MEM_STATIC, which is not recommended (see Chapter 2). Therefore, it is recommended to use dynamic memory for large calculations.

CIS_GUESS_DISK_TYPE

Determines the type of guesses to be read from disk

TYPE:

INTEGER

DEFAULT:

Nil

OPTIONS:

0

Read triplets only

1

Read triplets and singlets

2

Read singlets only

RECOMMENDATION:

Must be specified if CIS_GUESS_DISK is TRUE.

CIS_GUESS_DISK

Read the CIS guess from disk (previous calculation)

TYPE:

LOGICAL

DEFAULT:

False

OPTIONS:

False

Create a new guess

True

Read the guess from disk

RECOMMENDATION:

Requires a guess from previous calculation.

CIS_MOMENTS

Controls calculation of excited-state (CIS or TDDFT) multipole moments

TYPE:

LOGICAL/INTEGER

DEFAULT:

FALSE

(or 0)

OPTIONS:

FALSE

(or 0) Do not calculate excited-state moments.

TRUE

(or 1) Calculate moments for each excited state.

RECOMMENDATION:

Set to TRUE if excited-state moments are desired. (This is a trivial additional calculation.) The MULTIPOLE_ORDER controls how many multipole moments are printed.

CIS_MULLIKEN

Controls Mulliken and Löwdin population analyses for excited-state particle and hole density matrices.

TYPE:

LOGICAL/INTEGER

DEFAULT:

FALSE

OPTIONS:

FALSE

(or 0) Do not perform particle/hole population analysis.

TRUE

(or 1) Perform both Mulliken and Löwdin analysis of the particle and hole

density matrices for each excited state.

RECOMMENDATION:

Set to TRUE if desired. This represents a trivial additional calculation.

CIS_N_ROOTS

Sets the number of CI-Singles (CIS) excited state roots to find

TYPE:

INTEGER

DEFAULT:

0

Do not look for any excited states

OPTIONS:

$n$

$n> 0$ Looks for $n$ CIS excited states

RECOMMENDATION:

None

CIS_RELAXED_DENSITY

Use the relaxed CIS density for attachment/detachment density analysis

TYPE:

LOGICAL

DEFAULT:

False

OPTIONS:

False

Do not use the relaxed CIS density in analysis

True

Use the relaxed CIS density in analysis.

RECOMMENDATION:

None

CIS_S2_THRESH

Determines whether a state is singlet or triplet in unrestricted calculations.

TYPE:

INTEGER

DEFAULT:

120

OPTIONS:

None

RECOMMENDATION:

If set to 120, the states with $\langle \Hat {S}^2\rangle > 1.20$ are treated as triplet states, with other states are treated as singlets.

CIS_SINGLETS

Solve for singlet excited states in RCIS calculations (ignored for UCIS)

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

Solve for singlet states

FALSE

Do not solve for singlet states.

RECOMMENDATION:

None

CIS_STATE_DERIV

Sets CIS state for excited state optimizations and vibrational analysis

TYPE:

INTEGER

DEFAULT:

0

Does not select any of the excited states

OPTIONS:

$n$

Select the $n$ th state.

RECOMMENDATION:

Check to see that the states do no change order during an optimization

CIS_TRIPLETS

Solve for triplet excited states in RCIS calculations (ignored for UCIS)

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

Solve for triplet states

FALSE

Do not solve for triplet states.

RECOMMENDATION:

None

CM5

Controls running of CM5 population analysis.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Calculate CM5 populations.

FALSE

Do not calculate CM5 populations.

RECOMMENDATION:

None

COMPLEX_CCMAN

Requests complex-scaled or CAP-augmented CC/EOM calculations.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Engage complex CC/EOM code.

RECOMMENDATION:

Not available in CCMAN. Need to specify CAP strength or complex-scaling parameter in $complex_ccman section.

CORE_CHARACTER

Selects how the core orbitals are determined in the frozen-core approximation.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Use energy-based definition.

1-4

Use Mulliken-based definition (see Table 5.3.2 for details).

RECOMMENDATION:

Use default, unless performing calculations on molecules with heavy elements.

CORRELATION

Specifies the correlation level of theory, either DFT or wavefunction-based.

TYPE:

STRING

DEFAULT:

None

No Correlation

OPTIONS:

None

No Correlation.

VWN

Vosko-Wilk-Nusair parameterization #5

LYP

Lee-Yang-Parr

PW91, PW

GGA91 (Perdew)

PW92

LSDA 92 (Perdew and Wang) [46]

PK09

LSDA (Proynov-Kong) [47]

LYP(EDF1)

LYP(EDF1) parameterization

Perdew86, P86

Perdew 1986

PZ81, PZ

Perdew-Zunger 1981

PBE

Perdew-Burke-Ernzerhof 1996

TPSS

The correlation component of the TPSS functional

B94

Becke 1994 correlation in fully analytic form

B94hyb

Becke 1994 correlation as above, but readjusted for use only within the hybrid scheme BR89B94hyb

PK06

Proynov-Kong 2006 correlation (known also as “tLap”

(B88)OP

OP correlation [80], optimized for use with B88 exchange

(PBE)OP

OP correlation [80], optimized for use with PBE exchange

Wigner

Wigner

MP2

Local_MP2

Local MP2 calculations (TRIM and DIM models)

CIS(D)

MP2-level correction to CIS for excited states

MP3

MP4SDQ

MP4

CCD

CCD(2)

CCSD

CCSD(T)

CCSD(2)

QCISD

QCISD(T)

OD

OD(T)

OD(2)

VOD

VOD(2)

QCCD

VQCCD

RECOMMENDATION:

Consult the literature and reviews for guidance.

CORRELATION

Specifies the correlation level of theory handled by CCMAN/CCMAN2.

TYPE:

STRING

DEFAULT:

None

No Correlation

OPTIONS:

CCMP2

Regular MP2 handled by CCMAN/CCMAN2

MP3

CCMAN and CCMAN2

MP4SDQ

CCMAN

MP4

CCMAN

CCD

CCMAN and CCMAN2

CCD(2)

CCMAN

CCSD

CCMAN and CCMAN2

CCSD(T)

CCMAN and CCMAN2

CCSD(2)

CCMAN

CCSD(fT)

CCMAN

CCSD(dT)

CCMAN

QCISD

CCMAN and CCMAN2

QCISD(T)

CCMAN and CCMAN2

OD

CCMAN

OD(T)

CCMAN

OD(2)

CCMAN

VOD

CCMAN

VOD(2)

CCMAN

QCCD

CCMAN

QCCD(T)

CCMAN

QCCD(2)

CCMAN

VQCCD

CCMAN

VQCCD(T)

CCMAN

VQCCD(2)

CCMAN

RECOMMENDATION:

Consult the literature for guidance.

CPSCF_NSEG

Controls the number of segments used to calculate the CPSCF equations.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not solve the CPSCF equations in segments.

$n$

User-defined. Use $n$ segments when solving the CPSCF equations.

RECOMMENDATION:

Use default.

CUBEFILE_STATE

Determines which excited state is used to generate cube files

TYPE:

INTEGER

DEFAULT:

None

OPTIONS:

$n$

Generate cube files for the $n$ th excited state

RECOMMENDATION:

None

CUDA_RI-MP2

Enables GPU implementation of RI-MP2

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

GPU-enabled MGEMM off

TRUE

GPU-enabled MGEMM on

RECOMMENDATION:

Necessary to set to 1 in order to run GPU-enabled RI-MP2

CUTOCC

Specifies occupied orbital cutoff

TYPE:

INTEGER: CUTOFF=CUTOCC/100

DEFAULT:

50

OPTIONS:

0-200

RECOMMENDATION:

None

CUTVIR

Specifies virtual orbital cutoff

TYPE:

INTEGER: CUTOFF=CUTVIR/100

DEFAULT:

0

No truncation

OPTIONS:

0-100

RECOMMENDATION:

None

CVGLIN

Convergence criterion for solving linear equations by the conjugate gradient iterative method (relevant if LINEQ=1 or 2).

TYPE:

FLOAT

DEFAULT:

1.0E-7

OPTIONS:

Real number specifying the actual criterion.

RECOMMENDATION:

The default value should be used unless convergence problems arise.

DEUTERATE

Requests that all hydrogen atoms be replaces with deuterium.

TYPE:

LOGICAL

DEFAULT:

FALSE

Do not replace hydrogens.

OPTIONS:

TRUE

Replace hydrogens with deuterium.

RECOMMENDATION:

Replacing hydrogen atoms reduces the fastest vibrational frequencies by a factor of 1.4, which allow for a larger fictitious mass and time step in ELMD calculations. There is no reason to replace hydrogens in BOMD calculations.

DFPT_EXCHANGE

Specifies the secondary functional in a HFPC/DFPC calculation.

TYPE:

STRING

DEFAULT:

None

OPTIONS:

None

RECOMMENDATION:

See reference for recommended basis set, functional, and grid pairings.

DFPT_XC_GRID

Specifies the secondary grid in a HFPC/DFPC calculation.

TYPE:

STRING

DEFAULT:

None

OPTIONS:

None

RECOMMENDATION:

See reference for recommended basis set, functional, and grid pairings.

DFTVDW_ALPHA1

Parameter in XDM calculation with higher-order terms

TYPE:

INTEGER

DEFAULT:

83

OPTIONS:

10-1000

RECOMMENDATION:

none

DFTVDW_ALPHA2

Parameter in XDM calculation with higher-order terms.

TYPE:

INTEGER

DEFAULT:

155

OPTIONS:

10-1000

RECOMMENDATION:

none

DFTVDW_JOBNUMBER

Basic vdW job control

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not apply the XDM scheme.

1

add vdW as energy/gradient correction to SCF.

2

add VDW as a DFT functional and do full SCF (this option only works with C6 XDM formula).

RECOMMENDATION:

none

DFTVDW_KAI

Damping factor K for C6 only damping function

TYPE:

INTEGER

DEFAULT:

800

OPTIONS:

10-1000

default 800

RECOMMENDATION:

none

DFTVDW_METHOD

Choose the damping function used in XDM

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

1

use Becke’s damping function including C6 term only.

2

use Becke’s damping function with higher-order (C8,C10) terms.

RECOMMENDATION:

none

DFTVDW_MOL1NATOMS

The number of atoms in the first monomer in dimer calculation

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0-NATOMS

default 0

RECOMMENDATION:

none

DFTVDW_PRINT

Printing control for VDW code

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

0 no printing.

1

minimum printing (default)

2

debug printing

RECOMMENDATION:

none

DFTVDW_USE_ELE_DRV

Specify whether to add the gradient correction to the XDM energy. only valid with Becke’s C6 damping function using the interpolated BR89 model.

TYPE:

LOGICAL

DEFAULT:

1

OPTIONS:

1

use density correction when applicable (default).

0

do not use this correction (for debugging purpose)

RECOMMENDATION:

none

DFT_D3_3BODY

Controls whether the three-body interaction in Grimme’s DFT-D3 method should be applied (see Eq. (14) in Ref. Grimme:2010).

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

(or 0) Do not apply the three-body interaction term

TRUE

Apply the three-body interaction term

RECOMMENDATION:

NONE

DFT_D3_RS6

Controls the strength of dispersion corrections, s $_{r,6}$ , in the Grimme’s DFT-D3 method (see Table IV in Ref. Grimme:2010).

TYPE:

INTEGER

DEFAULT:

1000

OPTIONS:

n

Corresponding to $s_{r6} = n/1000$ .

RECOMMENDATION:

NONE

DFT_D3_RS8

Controls the strength of dispersion corrections, $s_{r,8}$ , in Grimme’s DFT-D3 method (see Equation (4) in Ref. Grimme:2010).

TYPE:

INTEGER

DEFAULT:

1000

OPTIONS:

n

Corresponding to $s_{r,8} = n/1000$ .

RECOMMENDATION:

NONE

DFT_D3_S6

Controls the strength of dispersion corrections, $s_6$ , in Grimme’s DFT-D3 method (see Table IV in Ref. Grimme:2010).

TYPE:

INTEGER

DEFAULT:

1000

OPTIONS:

n

Corresponding to $s_6 = n/1000$ .

RECOMMENDATION:

NONE

DFT_D3_S8

Controls the strength of dispersion corrections, $s_8$ , in Grimme’s DFT-D3 method (see Table IV in Ref. Grimme:2010).

TYPE:

INTEGER

DEFAULT:

1000

OPTIONS:

n

Corresponding to $s_8 = n/1000$ .

RECOMMENDATION:

NONE

DFT_D_A

Controls the strength of dispersion corrections in the Chai-Head-Gordon DFT-D scheme in Eq.(3) of Ref. Chai:2008b.

TYPE:

INTEGER

DEFAULT:

600

OPTIONS:

n

Corresponding to $a = n/100$ .

RECOMMENDATION:

Use default, i.e., $a=6.0$

DFT_D

Controls the application of DFT-D or DFT-D3 scheme.

TYPE:

LOGICAL

DEFAULT:

None

OPTIONS:

FALSE

(or 0) Do not apply the DFT-D or DFT-D3 scheme

EMPIRICAL_GRIMME

dispersion correction from Grimme

EMPIRICAL_CHG

dispersion correction from Chai and Head-Gordon

EMPIRICAL_GRIMME3

dispersion correction from Grimme’s DFT-D3 method

(see Section 4.3.8)

RECOMMENDATION:

NONE

DH

Controls the application of DH-DFT scheme.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

(or 0) Do not apply the DH-DFT scheme

TRUE

(or 1) Apply DH-DFT scheme

RECOMMENDATION:

NONE

DIELST

The static dielectric constant.

TYPE:

FLOAT

DEFAULT:

78.39

OPTIONS:

real number specifying the constant.

RECOMMENDATION:

The default value 78.39 is appropriate for water solvent.

DIIS_ERR_RMS

Changes the DIIS convergence metric from the maximum to the RMS error.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE, FALSE

RECOMMENDATION:

Use default, the maximum error provides a more reliable criterion.

DIIS_PRINT

Controls the output from DIIS SCF optimization.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Minimal print out.

1

Chosen method and DIIS coefficients and solutions.

2

Level 1 plus changes in multipole moments.

3

Level 2 plus Multipole moments.

4

Level 3 plus extrapolated Fock matrices.

RECOMMENDATION:

Use default

DIIS_SEPARATE_ERRVEC

Control optimization of DIIS error vector in unrestricted calculations.

TYPE:

LOGICAL

DEFAULT:

FALSE

Use a combined alpha and beta error vector.

OPTIONS:

FALSE

Use a combined alpha and beta error vector.

TRUE

Use separate error vectors for the alpha and beta spaces.

RECOMMENDATION:

When using DIIS in Q-Chem a convenient optimization for unrestricted calculations is to sum the alpha and beta error vectors into a single vector which is used for extrapolation. This is often extremely effective, but in some pathological systems with symmetry breaking, can lead to false solutions being detected, where the alpha and beta components of the error vector cancel exactly giving a zero DIIS error. While an extremely uncommon occurrence, if it is suspected, set DIIS_SEPARATE_ERRVEC to TRUE to check.

DIIS_SUBSPACE_SIZE

Controls the size of the DIIS and/or RCA subspace during the SCF.

TYPE:

INTEGER

DEFAULT:

15

OPTIONS:

User-defined

RECOMMENDATION:

None

DIP_SINGLETS

Sets the number of singlet DIP roots to find. Valid only for closed-shell references.

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any singlet DIP states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ DIP singlet states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

DIP_STATES

Sets the number of DIP roots to find. For closed-shell reference, defaults into DIP_SINGLETS. For open-shell references, specifies all low-lying states.

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any DIP states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ DIP states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

DIP_TRIPLETS

Sets the number of triplet DIP roots to find. Valid only for closed-shell references.

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any DIP triplet states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ DIP triplet states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

DIRECT_RI

Controls use of RI and Cholesky integrals in conventional (undecomposed) form

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE - use all integrals in decomposed format

TRUE - transform all RI or Cholesky integral back to conventional format

RECOMMENDATION:

By default all integrals are used in decomposed format allowing significant reduction of memory use. If all integrals are transformed back (TRUE option) no memory reduction is achieved and decomposition error is introduced, however, the integral transformation is performed significantly faster and conventional CC/EOM algorithms are used.

DIRECT_SCF

Controls direct SCF.

TYPE:

LOGICAL

DEFAULT:

Determined by program.

OPTIONS:

TRUE

Forces direct SCF.

FALSE

Do not use direct SCF.

RECOMMENDATION:

Use default; direct SCF switches off in-core integrals.

DMA_MIDPOINTS

Specifies whether to include bond midpoints into DMA expansion.

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

FALSE

Do not include bond midpoints.

TRUE

Include bond midpoint.

RECOMMENDATION:

None

DORAMAN

Controls calculation of Raman intensities. Requires JOBTYPE to be set to FREQ

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not calculate Raman intensities.

TRUE

Do calculate Raman intensities.

RECOMMENDATION:

None

DO_DMA

Specifies whether to perform Distributed Multipole Analysis.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Turn off DMA.

TRUE

Turn on DMA.

RECOMMENDATION:

None

DSF_STATES

Sets the number of doubly spin-flipped target states roots to find.

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any DSF states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ doubly spin-flipped states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

DUAL_BASIS_ENERGY

Activates dual-basis SCF (HF or DFT) energy correction.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

Analytic first derivative available for HF and DFT (see JOBTYPE)

Can be used in conjunction with MP2 or RI-MP2

See BASIS, BASIS2, BASISPROJTYPE

RECOMMENDATION:

Use Dual-Basis to capture large-basis effects at smaller basis cost. Particularly useful with RI-MP2, in which HF often dominates. Use only proper subsets for small-basis calculation.

D_CPSCF_PERTNUM

Specifies whether to do the perturbations one at a time, or all together.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Perturbed densities to be calculated all together.

1

Perturbed densities to be calculated one at a time.

RECOMMENDATION:

None

D_SCF_CONV_1

Sets the convergence criterion for the level-1 iterations. This preconditions the density for the level-2 calculation, and does not include any two-electron integrals.

TYPE:

INTEGER

DEFAULT:

4

corresponding to a threshold of $10^{-4}$ .

OPTIONS:

$n<10$

Sets convergence threshold to $10^{-n}$ .

RECOMMENDATION:

The criterion for level-1 convergence must be less than or equal to the level-2 criterion, otherwise the D-CPSCF will not converge.

D_SCF_CONV_2

Sets the convergence criterion for the level-2 iterations.

TYPE:

INTEGER

DEFAULT:

4

Corresponding to a threshold of $10^{-4}$ .

OPTIONS:

$n<10$

Sets convergence threshold to $10^{-n}$ .

RECOMMENDATION:

None

D_SCF_DIIS

Specifies the number of matrices to use in the DIIS extrapolation in the D-CPSCF.

TYPE:

INTEGER

DEFAULT:

11

OPTIONS:

$n$

$n$ = 0 specifies no DIIS extrapolation is to be used.

RECOMMENDATION:

Use the default.

D_SCF_MAX_1

Sets the maximum number of level-1 iterations.

TYPE:

INTEGER

DEFAULT:

100

OPTIONS:

$n$

User defined.

RECOMMENDATION:

Use default.

D_SCF_MAX_2

Sets the maximum number of level-2 iterations.

TYPE:

INTEGER

DEFAULT:

30

OPTIONS:

$n$ User defined.

RECOMMENDATION:

Use default.

EA_STATES

Sets the number of attached target states roots to find. By default, $\alpha$ electron will be attached (see EOM_EA_ALPHA).

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any EA states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ EA states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

ECP

Defines the effective core potential and associated basis set to be used

TYPE:

STRING

DEFAULT:

No pseudopotential

OPTIONS:

General, Gen

User defined. ($ecp keyword required)

Symbol

Use standard pseudopotentials discussed above.

RECOMMENDATION:

Pseudopotentials are recommended for first row transition metals and heavier elements. Consul the reviews for more details.

EDA_BSSE

Calculates the BSSE correction when performing the energy decomposition analysis.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

Set to TRUE unless a very large basis set is used.

EDA_COVP

Perform COVP analysis when evaluating the RS or ARS charge-transfer correction. COVP analysis is currently implemented only for systems of two fragments.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

Set to TRUE to perform COVP analysis in an EDA or SCF MI(RS) job.

EDA_PRINT_COVP

Replace the final MOs with the CVOP orbitals in the end of the run.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

Set to TRUE to print COVP orbitals instead of conventional MOs.

EE_SINGLETS

Sets the number of singlet excited state roots to find. Valid only for closed-shell references.

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any excited states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ excited states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

EE_STATES

Sets the number of excited state roots to find. For closed-shell reference, defaults into EE_SINGLETS. For open-shell references, specifies all low-lying states.

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any excited states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ excited states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

EE_TRIPLETS

Sets the number of triplet excited state roots to find. Valid only for closed-shell references.

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any excited states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ excited states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

EFP_COORD_XYZ

Use coordinates of three atoms instead of Euler angles to specify position and orientation of the fragments

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE FALSE

RECOMMENDATION:

None

EFP_DIRECT_POLARIZATION_DRIVER

Use direct solver for EFP polarization

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE FALSE

RECOMMENDATION:

Direct polarization solver provides stable convergence of induced dipoles which may otherwise become problematic in case of closely lying or highly polar or charged fragments. The computational cost of direct polarization versus iterative polarization becomes higher for systems containing more than 10000 polarizable points.

EFP_DISP_DAMP

Controls fragment-fragment dispersion screening in EFP

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

0

switch off dispersion screening

1

use Tang-Toennies screening, with fixed parameter b=1.5

2

use overlap-based damping

RECOMMENDATION:

None

EFP_DISP

Controls fragment-fragment dispersion in EFP

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

switch off dispersion

FALSE

switch off dispersion

RECOMMENDATION:

None

EFP_ELEC_DAMP

Controls fragment-fragment electrostatic screening in EFP

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

0

switch off electrostatic screening

1

use overlap-based damping correction

2

use exponential damping correction if screening parameters are provided in the EFP potential

RECOMMENDATION:

Overlap-based damping is recommended

EFP_ELEC

Controls fragment-fragment electrostatics in EFP

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

switch on electrostatics

FALSE

switch off electrostatics

RECOMMENDATION:

None

EFP_ENABLE_LINKS

Enable fragment links in EFP region

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE FALSE

RECOMMENDATION:

None

EFP_EXREP

Controls fragment-fragment exchange repulsion in EFP

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

switch on exchange repulsion

FALSE

switch off exchange repulsion

RECOMMENDATION:

None

EFP_FRAGMENTS_ONLY

Specifies whether there is a QM part

TYPE:

LOGICAL

DEFAULT:

FALSE

QM part is present

OPTIONS:

TRUE

Only MM part is present: all fragments are treated by EFP

FALSE

QM part is present: do QM/MM EFP calculation

RECOMMENDATION:

None

EFP_INPUT

Specifies the format of EFP input

TYPE:

LOGICAL

DEFAULT:

FALSE

Dummy atom (e.g., He) in $molecule section should be present

OPTIONS:

TRUE

A format without dummy atom in $molecule section

FALSE

A format with dummy atom in $molecule section

RECOMMENDATION:

None

EFP_POL_DAMP

Controls fragment-fragment polarization screening in EFP

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

0

switch off polarization screening

1

use Tang-Toennies screening

RECOMMENDATION:

None

EFP_POL

Controls fragment-fragment polarization in EFP

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

switch on polarization

FALSE

switch off polarization

RECOMMENDATION:

None

EFP_QM_DISP

Controls QM-EFP dispersion

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

switch on QM-EFP dispersion

FALSE

switch off QM-EFP dispersion

RECOMMENDATION:

None

EFP_QM_ELEC_DAMP

Controls QM-EFP electrostatics screening in EFP

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

switch off electrostatic screening

1

use overlap based damping correction

RECOMMENDATION:

None

EFP_QM_ELEC

Controls QM-EFP electrostatics

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

switch on QM-EFP electrostatics

FALSE

switch off QM-EFP electrostatics

RECOMMENDATION:

None

EFP_QM_EXREP

Controls QM-EFP exchange-repulsion

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

switch on QM-EFP exchange-repulsion

FALSE

switch off QM-EFP exchange-repulsion

RECOMMENDATION:

None

EFP_QM_POL

Controls QM-EFP polarization

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

switch on QM-EFP polarization

FALSE

switch off QM-EFP polarization

RECOMMENDATION:

None

EFP

Specifies that EFP calculation is requested

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE FALSE

RECOMMENDATION:

The keyword should be present if excited state calculation is requested

EMBEDMAN

Turns density embedding on.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not use density embedding.

1

Turn on density embedding.

RECOMMENDATION:

Use EMBEDMAN for QM/QM density embedded calculations.

EMBED_MU

Specifies exponent value of projection operator scaling factor, $\mu$ [Eq. eq:des_fock and eq:des_corr].

TYPE:

INTEGER

DEFAULT:

7

OPTIONS:

n

$\mu = 10^{n}$ .

RECOMMENDATION:

Values of 2 - 7 are recommended. A higher value of $\mu$ leads to better orthogonality of the fragment MOs. but $\mu > 10^{7}$ introduces numerical noise. $\mu < 10^{2}$ results in non-additive terms becoming too large. Energy corrections are fairly insensitive to changes in $\mu$ within the range of $10^{2} - 10^{7}$ .

EMBED_THEORY

Specifies post-DFT method performed on fragment one.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

No post HF method, only DFT on fragment one.

1

Perform CCSD(T) calculation on fragment one.

2

Perform MP2 calculation on fragment one.

RECOMMENDATION:

This should be 1 or 2 for the high-level QM calculation of fragment 1-in-2, and 0 for fragment 2-in-1 low-level QM calculation.

EMBED_THRESH

Specifies threshold cutoff for AO contribution used to determine which MOs belong to which fragments

TYPE:

INTEGER

DEFAULT:

500

OPTIONS:

n

Threshold $= n/1000$

RECOMMENDATION:

Acceptable values range from 0 to 1000. Should only need to be tuned for non-highly localized MOs

EOM_CORR

Specifies the correlation level.

TYPE:

STRING

DEFAULT:

None

No correction will be computed

OPTIONS:

SD(DT)

EOM-CCSD(dT), available for EE, SF, and IP

SD(FT)

EOM-CCSD(fT), available for EE, SF, and IP

SD(ST)

EOM-CCSD(sT), available for IP

RECOMMENDATION:

None

EOM_DAVIDSON_CONVERGENCE

Convergence criterion for the RMS residuals of excited state vectors

TYPE:

INTEGER

DEFAULT:

5

Corresponding to $10^{-5}$

OPTIONS:

$n$

Corresponding to $10^{-n}$ convergence criterion

RECOMMENDATION:

Use default. Should normally be set to the same value as EOM_DAVIDSON_THRESHOLD.

EOM_DAVIDSON_MAXVECTORS

Specifies maximum number of vectors in the subspace for the Davidson diagonalization.

TYPE:

INTEGER

DEFAULT:

60

OPTIONS:

$n$

Up to $n$ vectors per root before the subspace is reset

RECOMMENDATION:

Larger values increase disk storage but accelerate and stabilize convergence.

EOM_DAVIDSON_MAX_ITER

Maximum number of iteration allowed for Davidson diagonalization procedure.

TYPE:

INTEGER

DEFAULT:

30

OPTIONS:

$n$

User-defined number of iterations

RECOMMENDATION:

Default is usually sufficient

EOM_DAVIDSON_THRESHOLD

Specifies threshold for including a new expansion vector in the iterative Davidson diagonalization. Their norm must be above this threshold.

TYPE:

INTEGER

DEFAULT:

00105

Corresponding to 0.00001

OPTIONS:

$abcde$

Integer code is mapped to $abc\times 10^{-de}$

RECOMMENDATION:

Use default unless converge problems are encountered. Should normally be set to the same values as EOM_DAVIDSON_CONVERGENCE, if convergence problems arise try setting to a value less than EOM_DAVIDSON_CONVERGENCE.

EOM_EA_ALPHA

Sets the number of attached target states derived by attaching $\alpha$ electron (M $_ s$ = ${{1}\over {2}}$ , default in EOM-EA).

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any EA states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ EA states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

EOM_EA_BETA

Sets the number of attached target states derived by attaching $\beta$ electron (M $_ s$ = $-{{1}\over {2}}$ , EA-SF).

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any EA states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ EA states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

EOM_FAKE_IPEA

If TRUE, calculates fake EOM-IP or EOM-EA energies and properties using the diffuse orbital trick. Default for EOM-EA and Dyson orbital calculations in CCMAN.

TYPE:

LOGICAL

DEFAULT:

FALSE (use proper EOM-IP code)

OPTIONS:

FALSE, TRUE

RECOMMENDATION:

None. This feature only works for CCMAN.

EOM_GPLMR_MSUBSIZE

Specifies the number of Krylov-space residuals in GPLMR.

TYPE:

INTEGER

DEFAULT:

3

OPTIONS:

$n$

Generate $n$ residuals at each iteration.

RECOMMENDATION:

Use default. The convergence is faster for larger $n$ , but the memory usage and the overall cost will increase.

EOM_GPLMR

Specifies whether to engage GPLMR solver in EOM calculations.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Use GPLMR.

RECOMMENDATION:

Not available in CCMAN.

EOM_IPEA_FILTER

If TRUE, filters the EOM-IP/EA amplitudes obtained using the diffuse orbital implementation (see EOM_FAKE_IPEA). Helps with convergence.

TYPE:

LOGICAL

DEFAULT:

FALSE (EOM-IP or EOM-EA amplitudes will not be filtered)

OPTIONS:

FALSE, TRUE

RECOMMENDATION:

None

EOM_IP_ALPHA

Sets the number of ionized target states derived by removing $\alpha$ electron (M $_ s$ = $-{{1}\over {2}}$ ).

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any IP/ $\alpha$ states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ ionized states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

EOM_IP_BETA

Sets the number of ionized target states derived by removing $\beta$ electron (M $_ s$ = ${{1}\over {2}}$ , default for EOM-IP).

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any IP/ $\beta$ states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ ionized states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

EOM_NGUESS_DOUBLES

Specifies number of excited state guess vectors which are double excitations.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

Include $n$ guess vectors that are double excitations

RECOMMENDATION:

This should be set to the expected number of doubly excited states (see also EOM_PRECONV_DOUBLES), otherwise they may not be found.

EOM_NGUESS_SINGLES

Specifies number of excited state guess vectors that are single excitations.

TYPE:

INTEGER

DEFAULT:

Equal to the number of excited states requested

OPTIONS:

$n$

Include $n$ guess vectors that are single excitations

RECOMMENDATION:

Should be greater or equal than the number of excited states requested.

EOM_PRECONV_DOUBLES

When not zero, doubly excited vectors are converged prior to a full excited states calculation. Sets the maximum number of iterations for pre-converging procedure

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

do not pre-converge

N

perform N Davidson iterations pre-converging doubles.

RECOMMENDATION:

Occasionally necessary to ensure a doubly excited state is found. Also used in DSF calculations instead of EOM_PRECONV_SINGLES

EOM_PRECONV_SD

When not zero, EOM vectors are pre-converged prior to a full excited states calculation. Sets the maximum number of iterations for pre-converging procedure

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

do not pre-converge

N

perform N Davidson iterations pre-converging singles and doubles.

RECOMMENDATION:

Occasionally necessary to ensure that all low-lying states are found. Also, very useful in EOM(2,3) calculations.

None

EOM_PRECONV_SINGLES

When not zero, singly excited vectors are converged prior to a full excited states calculation. Sets the maximum number of iterations for pre-converging procedure

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

do not pre-converge

N

perform N Davidson iterations pre-converging singles.

RECOMMENDATION:

Sometimes helps with problematic convergence.

EOM_REF_PROP_TE

Request for calculation of non-relaxed two-particle EOM-CC properties. The two-particle properties currently include $\ensuremath{\langle }S^2\ensuremath{\rangle }$ . The one-particle properties also will be calculated, since the additional cost of the one-particle properties calculation is inferior compared to the cost of $\ensuremath{\langle }S^2\ensuremath{\rangle }$ . The variable CC_EOM_PROP must be also set to TRUE. Alternatively, CC_CALC_SSQ can be used to request $\ensuremath{\langle }S^2\ensuremath{\rangle }$ calculation.

TYPE:

LOGICAL

DEFAULT:

FALSE

(no two-particle properties will be calculated)

OPTIONS:

FALSE, TRUE

RECOMMENDATION:

The two-particle properties are computationally expensive since they require calculation and use of the two-particle density matrix (the cost is approximately the same as the cost of an analytic gradient calculation). Do not request the two-particle properties unless you really need them.

EOM_SHIFT

Specifies energy shift in EOM calculations.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

corresponds to $n\cdot 10^{-3}$ hartree shift (i.e., 11000 = 11 hartree); solve for eigenstates around this value.

RECOMMENDATION:

Not available in CCMAN.

EOM_USER_GUESS

Specifies if user-defined guess will be used in EOM calculations.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Solve for a state that has maximum overlap with a trans-n specified in $eom_user_guess.

RECOMMENDATION:

The orbitals are ordered by energy, as printed in the beginning of the CCMAN2 output. Not available in CCMAN.

EPAO_ITERATE

Controls iterations for EPAO calculations (see PAO_METHOD).

TYPE:

INTEGER

DEFAULT:

0

Use uniterated EPAOs based on atomic blocks of SPS.

OPTIONS:

$n$

Optimize the EPAOs for up to $n$ iterations.

RECOMMENDATION:

Use default. For molecules that are not too large, one can test the sensitivity of the results to the type of minimal functions by the use of optimized EPAOs in which case a value of $n=500$ is reasonable.

EPAO_WEIGHTS

Controls algorithm and weights for EPAO calculations (see PAO_METHOD).

TYPE:

INTEGER

DEFAULT:

115

Standard weights, use 1 $^{\ensuremath{\mathrm{st}}}$ and 2 $^{\ensuremath{\mathrm{nd}}}$ order optimization

OPTIONS:

15

Standard weights, with 1 $^{\ensuremath{\mathrm{st}}}$ order optimization only.

RECOMMENDATION:

Use default, unless convergence failure is encountered.

ERCALC

Specifies the Edmiston-Ruedenberg localized orbitals are to be calculated

TYPE:

INTEGER

DEFAULT:

06000

OPTIONS:

$aabcd$

$aa$

specifies the convergence threshold.

If $aa>3$ , the threshold is set to $10^{-aa}$ . The default is 6.

If $aa=1$ , the calculation is aborted after the guess, allowing Pipek-Mezey

orbitals to be extracted.

$b$

specifies the guess:

0 Boys localized orbitals. This is the default

1 Pipek-Mezey localized orbitals.

$c$

specifies restart options (if restarting from an ER calculation):

0 No restart. This is the default

1 Read in MOs from last ER calculation.

2 Read in MOs and RI integrals from last ER calculation.

$d$

specifies how to treat core orbitals

0 Do not perform ER localization. This is the default.

1 Localize core and valence together.

2 Do separate localizations on core and valence.

3 Localize only the valence electrons.

4 Use the $localize section.

RECOMMENDATION:

ERCALC 1 will usually suffice, which uses threshold $10^{-6}$ .

ER_CIS_NUMSTATE

Define how many states to mix with ER localized diabatization.

TYPE:

INTEGER

DEFAULT:

0

Do not perform ER localized diabatization.

OPTIONS:

1 to N where N is the number of CIS states requested (CIS_N_ROOTS)

RECOMMENDATION:

It is usually not wise to mix adiabatic states that are separated by more than a few eV or a typical reorganization energy in solvent.

ESP_TRANS

Controls the calculation of the electrostatic potential of the transition density

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

compute the electrostatic potential of the excited state transition density

FALSE

compute the electrostatic potential of the excited state electronic density

RECOMMENDATION:

NONE

EXCHANGE

Specifies the exchange functional or exchange-correlation functional for hybrid.

TYPE:

STRING

DEFAULT:

No default exchange functional

OPTIONS:

HF

Fock exchange

Slater, S

Slater (Dirac 1930)

ETheta_LDA, ETheta_LSDA

TAO-DFT local density approximation for $E_\theta$ [150]

(use in conjunction with another exchange functional)

Becke86, B86

Becke 1986

Becke, B, B88

Becke 1988

muB88

Short-range Becke exchange, as formulated by Song et al. [114]

Gill96, Gill

Gill 1996

GG99

Gilbert and Gill, 1999

Becke(EDF1), B(EDF1)

Becke (uses EDF1 parameters)

PW86,

Perdew-Wang 1986

rPW86,

Refitted PW86 for use in vdW-DF-10 and VV10

PW91, PW

Perdew-Wang 1991

PBE

Perdew-Burke-Ernzerhof 1996

AK13

Armiento and Kümmel, 2013 [63]

TPSS

The nonempirical exchange-correlation scheme of Tao,

Perdew, Staroverov, and Scuseria (requires also that the user

specify “TPSS” for correlation)

TPSSH

The hybrid version of TPSS (with no input line for correlation)

PBE0, PBE1PBE

PBE hybrid with 25% HF exchange

PBEOP

PBE exchange + one-parameter progressive correlation

wPBE

Short-range $\omega$ PBE exchange, as formulated by Henderson et al. [115]

muPBE

Short-range $\mu$ PBE exchange, due to Song et al. [114]

B97

Becke97 XC hybrid

B97-1

Becke97 re-optimized by Hamprecht et al.

B97-2

Becke97-1 optimized further by Wilson et al.

B3PW91, Becke3PW91, B3P

B3PW91 hybrid

B3LYP, Becke3LYP

B3LYP hybrid

B3LYP5

B3LYP based on correlation functional #5 of

HCTH

HCTH hybrid

HCTH-120

HCTH-120 hybrid

HCTH-147

HCTH-147 hybrid

HCTH-407

HCTH-407 hybrid

Vosko, Wilk, and Nusair rather than their functional #3

BOP

B88 exchange + one-parameter progressive correlation

EDF1

EDF1

EDF2

EDF2

VSXC

VSXC meta-GGA, not a hybrid

BMK

BMK hybrid

M05

M05 hybrid

M052X

M05-2X hybrid

M06L

M06-L hybrid

M06HF

M06-HF hybrid

M06

M06 hybrid

M062X

M06-2X hybrid

M08HX

M08-HX hybrid

M08SO

M08-SO hybrid

M11L

M11-L hybrid

M11

M11 long-range corrected hybrid

SOGGA

SOGGA hybrid

SOGGA11

SOGGA11 hybrid

SOGGA11X

SOGGA11-X hybrid

BR89

Becke-Roussel 1989 represented in analytic form

omegaB97

$\omega$ B97 long-range corrected hybrid

omegaB97X

$\omega$ B97X long-range corrected hybrid

omegaB97X-D

$\omega$ B97X-D long-range corrected hybrid with dispersion corrections

omegaB97X-2(LP)

$\omega$ B97X-2(LP) long-range corrected double-hybrid

omegaB97X-2(TQZ)

$\omega$ B97X-2(TQZ) long-range corrected double-hybrid

MCY2

The MCY2 hyper-GGA exchange-correlation

(with no input line for correlation)

B05

The hyper-GGA exchange-correlation functional

B05 with RI approximation for the exact-exchange energy

BM05

MB05 is based on RI-B05 but made it simpler,

and slightly more accurate.

PSTS

The hyper-GGA exchange-correlation functional

PSTS with RI approximation for the exact-exchange energy

density (with no input line for correlation)

PBE0_DH, PBE0_2

PBE double hybrid functionals, requires setting

CORRELATION to an MP2 implementation

General, Gen

User defined combination of K, X and C (refer next

section).

RECOMMENDATION:

Consult the literature to guide your selection.

FAST_XC

Controls direct variable thresholds to accelerate exchange correlation (XC) in DFT.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Turn FAST_XC on.

FALSE

Do not use FAST_XC.

RECOMMENDATION:

Caution: FAST_XC improves the speed of a DFT calculation, but may occasionally cause the SCF calculation to diverge.

FDIFF_DER

Controls what types of information are used to compute higher derivatives. The default uses a combination of energy, gradient and Hessian information, which makes the force field calculation faster.

TYPE:

INTEGER

DEFAULT:

3

for jobs where analytical 2nd derivatives are available.

0

for jobs with ECP.

OPTIONS:

0

Use energy information only.

1

Use gradient information only.

2

Use Hessian information only.

3

Use energy, gradient, and Hessian information.

RECOMMENDATION:

When the molecule is larger than benzene with small basis set, FDIFF_DER=2 may be faster. Note that FDIFF_DER will be set lower if analytic derivatives of the requested order are not available. Please refers to IDERIV.

FDIFF_STEPSIZE_QFF

Displacement used for calculating third and fourth derivatives by finite difference.

TYPE:

INTEGER

DEFAULT:

5291

Corresponding to 0.1 bohr. For calculating third and fourth derivatives.

OPTIONS:

$n$

Use a step size of $n\times 10^{-5}$ .

RECOMMENDATION:

Use default, unless on a very flat potential, in which case a larger value should be used.

FDIFF_STEPSIZE

Displacement used for calculating derivatives by finite difference.

TYPE:

INTEGER

DEFAULT:

100

Corresponding to 0.001 . For calculating second derivatives.

OPTIONS:

$n$

Use a step size of $n\times 10^{-5}$ .

RECOMMENDATION:

Use default, unless on a very flat potential, in which case a larger value should be used. See FDIFF_STEPSIZE_QFF for third and fourth derivatives.

FOA_FUNDGAP

Compute the frozen-orbital approximation of the fundamental gap.

TYPE:

Boolean

DEFAULT:

false

OPTIONS:

false

(default) do not compute FOA DD and fundamental gap

true

compute and print FOA fundamental gap information. Implies KS_GAP_PRINT.

RECOMMENDATION:

Use in conjuction with KS_GAP_UNIT if true.

FOCK_EXTRAP_ORDER

Specifies the polynomial order $N$ for Fock matrix extrapolation.

TYPE:

INTEGER

DEFAULT:

0

Do not perform Fock matrix extrapolation.

OPTIONS:

$N$

Extrapolate using an $N$ th-order polynomial ( $N > 0$ ).

RECOMMENDATION:

None

FOCK_EXTRAP_POINTS

Specifies the number $M$ of old Fock matrices that are retained for use in extrapolation.

TYPE:

INTEGER

DEFAULT:

0

Do not perform Fock matrix extrapolation.

OPTIONS:

$M$

Save $M$ Fock matrices for use in extrapolation $(M > N)$

RECOMMENDATION:

Higher-order extrapolations with more saved Fock matrices are faster and conserve energy better than low-order extrapolations, up to a point. In many cases, the scheme ( $N$ = 6, $M$ = 12), in conjunction with SCF_CONVERGENCE = 6, is found to provide about a 50% savings in computational cost while still conserving energy.

FON_E_THRESH

DIIS error below which occupations will be kept constant.

TYPE:

INTEGER

DEFAULT:

4

OPTIONS:

n

freeze occupations below DIIS error of $10^{-n}$

RECOMMENDATION:

This should be one or two numbers bigger than the desired SCF convergence threshold.

FON_NORB

Number of orbitals above and below the Fermi level that are allowed to have fractional occupancies.

TYPE:

INTEGER

DEFAULT:

4

OPTIONS:

n

number of active orbitals

RECOMMENDATION:

The number of valence orbitals is a reasonable choice.

FON_T_END

Final electronic temperature for FON calculation.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

Any desired final temperature.

RECOMMENDATION:

Pick the temperature to either reproduce experimental conditions (e.g. room temperature) or as low as possible to approach zero-temperature.

FON_T_METHOD

Selects cooling algorithm.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

1

temperature is scaled by a factor in each cycle

2

temperature is decreased by a constant number in each cycle

RECOMMENDATION:

We have made slightly better experience with a constant cooling rate. However, choose constant temperature when in doubt.

FON_T_SCALE

Determines the step size for the cooling.

TYPE:

INTEGER

DEFAULT:

90

OPTIONS:

n

temperature is scaled by $0.01 \cdot n$ in each cycle (cooling method 1)

n

temperature is decreased by n K in each cycle (cooling method 2)

RECOMMENDATION:

The cooling rate should be neither too slow nor too fast. Too slow may lead to final energies that are at undesirably high temperatures. Too fast may lead to convergence issues. Reasonable choices for methods 1 and 2 are 98 and 50, respectively. When in doubt, use constant temperature.

FON_T_START

Initial electronic temperature (in K) for FON calculation.

TYPE:

INTEGER

DEFAULT:

1000

OPTIONS:

Any desired initial temperature.

RECOMMENDATION:

Pick the temperature to either reproduce experimental conditions (e.g. room temperature) or as low as possible to approach zero-temperature.

FORCE_FIELD

Specifies the force field for MM energies in QM/MM calculations.

TYPE:

STRING

DEFAULT:

NONE

OPTIONS:

AMBER99

AMBER99 force field

CHARMM27

CHARMM27 force field

OPLSAA

OPLSAA force field

RECOMMENDATION:

None.

FRGM_LPCORR

Specifies a correction method performed after the locally-projected equations are converged.

TYPE:

STRING

DEFAULT:

NONE

OPTIONS:

ARS

Approximate Roothaan-step perturbative correction.

RS

Single Roothaan-step perturbative correction.

EXACT_SCF

Full SCF variational correction.

ARS_EXACT_SCF

Both ARS and EXACT_SCF in a single job.

RS_EXACT_SCF

Both RS and EXACT_SCF in a single job.

RECOMMENDATION:

For large basis sets use ARS, use RS if ARS fails.

FRGM_METHOD

Specifies a locally-projected method.

TYPE:

STRING

DEFAULT:

NONE

OPTIONS:

STOLL

Locally-projected SCF equations of Stoll are solved.

GIA

Locally-projected SCF equations of Gianinetti are solved.

NOSCF_RS

Single Roothaan-step correction to the FRAGMO initial guess.

NOSCF_ARS

Approximate single Roothaan-step correction to the FRAGMO initial guess.

NOSCF_DRS

Double Roothaan-step correction to the FRAGMO initial guess.

NOSCF_RS_FOCK

Non-converged SCF energy of the single Roothaan-step MOs.

RECOMMENDATION:

STOLL and GIA are for variational optimization of the ALMOs. NOSCF options are for computationally fast corrections of the FRAGMO initial guess.

FSM_MODE

Specifies the method of interpolation

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

1

Cartesian

2

LST

RECOMMENDATION:

2. In most cases, LST is superior to Cartesian interpolation.

FSM_NGRAD

Specifies the number of perpendicular gradient steps used to optimize each node

TYPE:

INTEGER

DEFAULT:

Undefined

OPTIONS:

N

number of perpendicular gradients per node

RECOMMENDATION:

4. Anything between 2 and 6 should work, where increasing the number is only needed for difficult reaction paths.

FSM_NNODE

Specifies the number of nodes along the string

TYPE:

INTEGER

DEFAULT:

Undefined

OPTIONS:

N

number of nodes in FSM calculation

RECOMMENDATION:

15. Use 10 to 20 nodes for a typical calculation. Reaction paths that connect multiple elementary steps should be separated into individual elementary steps, and one FSM job run for each pair of intermediates. Use a higher number when the FSM is followed by an approximate-Hessian based transition state search (Section 9.7).

FSM_OPT_MODE

Specifies the method of optimization

TYPE:

INTEGER

DEFAULT:

Undefined

OPTIONS:

1

Conjugate gradients

2

Quasi-Newton method with BFGS Hessian update

RECOMMENDATION:

2. The quasi-Newton method is more efficient when the number of nodes is high.

FTC_CLASS_THRESH_MULT

Together with FTC_CLASS_THRESH_ORDER, determines the cutoff threshold for included a shell-pair in the $dd$ class, i.e., the class that is expanded in terms of plane waves.

TYPE:

INTEGER

DEFAULT:

5

Multiplicative part of the FTC classification threshold. Together with

the default value of the FTC_CLASS_THRESH_ORDER this leads to

the $5\times 10^{-5}$ threshold value.

OPTIONS:

$n$ User specified.

RECOMMENDATION:

Use the default. If diffuse basis sets are used and the molecule is relatively big then tighter FTC classification threshold has to be used. According to our experiments using Pople-type diffuse basis sets, the default $5\times 10^{-5}$ value provides accurate result for an alanine5 molecule while $1\times 10^{-5}$ threshold value for alanine10 and $5\times 10^{-6}$ value for alanine15 has to be used.

FTC_CLASS_THRESH_ORDER

Together with FTC_CLASS_THRESH_MULT, determines the cutoff threshold for included a shell-pair in the $dd$ class, i.e., the class that is expanded in terms of plane waves.

TYPE:

INTEGER

DEFAULT:

5

Logarithmic part of the FTC classification threshold. Corresponds to $10^{-5}$

OPTIONS:

$n$

User specified

RECOMMENDATION:

Use the default.

FTC_SMALLMOL

Controls whether or not the operator is evaluated on a large grid and stored in memory to speed up the calculation.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

1

Use a big pre-calculated array to speed up the FTC calculations

0

Use this option to save some memory

RECOMMENDATION:

Use the default if possible and use 0 (or buy some more memory) when needed.

FTC

Controls the overall use of the FTC.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not use FTC in the Coulomb part

1

Use FTC in the Coulomb part

RECOMMENDATION:

Use FTC when bigger and/or diffuse basis sets are used.

GAUSSIAN_BLUR

Enables the use of Gaussian-delocalized external charges in a QM/MM calculation.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Delocalizes external charges with Gaussian functions.

FALSE

Point charges

RECOMMENDATION:

None

GAUSS_BLUR_WIDTH

Delocalization width for external MM Gaussian charges in a Janus calculations.

TYPE:

INTEGER

DEFAULT:

NONE

OPTIONS:

$n$

Use a width of $n \times 10^{-4}$ .

RECOMMENDATION:

Blur all MM external charges in a QM/MM calculation with the specified width. Gaussian blurring is currently incompatible with PCM calculations. Values of 1.0–2.0 are recommended in Ref. Das:2002.

GEOM_OPT_COORDS

Controls the type of optimization coordinates.

TYPE:

INTEGER

DEFAULT:

-1

OPTIONS:

0

Optimize in Cartesian coordinates.

1

Generate and optimize in internal coordinates, if this fails abort.

-1

Generate and optimize in internal coordinates, if this fails at any stage of the

optimization, switch to Cartesian and continue.

2

Optimize in $Z$ -matrix coordinates, if this fails abort.

-2

Optimize in $Z$ -matrix coordinates, if this fails during any stage of the

optimization switch to Cartesians and continue.

RECOMMENDATION:

Use the default; delocalized internals are more efficient.

GEOM_OPT_DMAX

Maximum allowed step size. Value supplied is multiplied by 10 $^{-3}$ .

TYPE:

INTEGER

DEFAULT:

300

= 0.3

OPTIONS:

$n$

User-defined cutoff.

RECOMMENDATION:

Use default.

GEOM_OPT_HESSIAN

Determines the initial Hessian status.

TYPE:

STRING

DEFAULT:

DIAGONAL

OPTIONS:

DIAGONAL

Set up diagonal Hessian.

READ

Have exact or initial Hessian. Use as is if Cartesian, or transform

if internals.

RECOMMENDATION:

An accurate initial Hessian will improve the performance of the optimizer, but is expensive to compute.

GEOM_OPT_LINEAR_ANGLE

Threshold for near linear bond angles (degrees).

TYPE:

INTEGER

DEFAULT:

165 degrees.

OPTIONS:

$n$

User-defined level.

RECOMMENDATION:

Use default.

GEOM_OPT_MAX_CYCLES

Maximum number of optimization cycles.

TYPE:

INTEGER

DEFAULT:

50

OPTIONS:

$n$

User defined positive integer.

RECOMMENDATION:

The default should be sufficient for most cases. Increase if the initial guess geometry is poor, or for systems with shallow potential wells.

GEOM_OPT_MAX_DIIS

Controls maximum size of subspace for GDIIS.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not use GDIIS.

-1

Default size = min(NDEG, NATOMS, 4) NDEG = number of molecular

degrees of freedom.

$n$

Size specified by user.

RECOMMENDATION:

Use default or do not set $n$ too large.

GEOM_OPT_MODE

Determines Hessian mode followed during a transition state search.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Mode following off.

$n$

Maximize along mode $n$ .

RECOMMENDATION:

Use default, for geometry optimizations.

GEOM_OPT_PRINT

Controls the amount of Optimize print output.

TYPE:

INTEGER

DEFAULT:

3

Error messages, summary, warning, standard information and gradient print out.

OPTIONS:

0

Error messages only.

1

Level 0 plus summary and warning print out.

2

Level 1 plus standard information.

3

Level 2 plus gradient print out.

4

Level 3 plus Hessian print out.

5

Level 4 plus iterative print out.

6

Level 5 plus internal generation print out.

7

Debug print out.

RECOMMENDATION:

Use the default.

GEOM_OPT_SYMFLAG

Controls the use of symmetry in Optimize.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

1

Make use of point group symmetry.

0

Do not make use of point group symmetry.

RECOMMENDATION:

Use default.

GEOM_OPT_TOL_DISPLACEMENT

Convergence on maximum atomic displacement.

TYPE:

INTEGER

DEFAULT:

1200 $\equiv 1200 \times 10^{-6}$ tolerance on maximum atomic displacement.

OPTIONS:

$n$

Integer value (tolerance = $n \times 10^{-6}$ ).

RECOMMENDATION:

Use the default. To converge GEOM_OPT_TOL_GRADIENT and one of GEOM_OPT_TOL_DISPLACEMENT and GEOM_OPT_TOL_ENERGY must be satisfied.

GEOM_OPT_TOL_ENERGY

Convergence on energy change of successive optimization cycles.

TYPE:

INTEGER

DEFAULT:

100 $\equiv 100 \times 10^{-8}$ tolerance on maximum gradient component.

OPTIONS:

$n$ Integer value (tolerance = value $n \times 10^{-8}$ ).

RECOMMENDATION:

Use the default. To converge GEOM_OPT_TOL_GRADIENT and one of GEOM_OPT_TOL_DISPLACEMENT and GEOM_OPT_TOL_ENERGY must be satisfied.

GEOM_OPT_TOL_GRADIENT

Convergence on maximum gradient component.

TYPE:

INTEGER

DEFAULT:

300

$\equiv 300\times 10^{-6}$ tolerance on maximum gradient component.

OPTIONS:

$n$

Integer value (tolerance = $n \times 10^{-6}$ ).

RECOMMENDATION:

Use the default. To converge GEOM_OPT_TOL_GRADIENT and one of GEOM_OPT_TOL_DISPLACEMENT and GEOM_OPT_TOL_ENERGY must be satisfied.

GEOM_OPT_UPDATE

Controls the Hessian update algorithm.

TYPE:

INTEGER

DEFAULT:

-1

OPTIONS:

-1

Use the default update algorithm.

0

Do not update the Hessian (not recommended).

1

Murtagh-Sargent update.

2

Powell update.

3

Powell/Murtagh-Sargent update (TS default).

4

BFGS update (OPT default).

5

BFGS with safeguards to ensure retention of positive definiteness

(GDISS default).

RECOMMENDATION:

Use default.

GEOM_PRINT

Controls the amount of geometric information printed at each step.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Prints out all geometric information; bond distances, angles, torsions.

FALSE

Normal printing of distance matrix.

RECOMMENDATION:

Use if you want to be able to quickly examine geometric parameters at the beginning and end of optimizations. Only prints in the beginning of single point energy calculations.

GRAIN

Controls the number of lowest-level boxes in one dimension for CFMM.

TYPE:

INTEGER

DEFAULT:

-1

Program decides best value, turning on CFMM when useful

OPTIONS:

-1

Program decides best value, turning on CFMM when useful

1

Do not use CFMM

$n\ge 8$

Use CFMM with $n$ lowest-level boxes in one dimension

RECOMMENDATION:

This is an expert option; either use the default, or use a value of 1 if CFMM is not desired.

GVB_AMP_SCALE

Scales the default orbital amplitude iteration step size by $n$ /1000 for IP/RCC. PP amplitude equations are solved analytically, so this parameter does not affect PP.

TYPE:

INTEGER

DEFAULT:

1000

Corresponding to 100%

OPTIONS:

$n$

User-defined, 0–1000

RECOMMENDATION:

Default is usually fine, but in some highly-correlated systems it can help with convergence to use smaller values.

GVB_DO_ROHF

Sets the number of Unrestricted-in-Active Pairs to be kept restricted.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-Defined

RECOMMENDATION:

If $n$ is the same value as GVB_N_PAIRS returns the ROHF solution for GVB, only works with the UNRESTRICTED=TRUE implementation of GVB with GVB_OLD_UPP=0 (it’s default value)

GVB_DO_SANO

Sets the scheme used in determining the active virtual orbitals in a Unrestricted-in-Active Pairs GVB calculation.

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

0

No localization or Sano procedure

1

Only localizes the active virtual orbitals

2

Uses the Sano procedure

RECOMMENDATION:

Different initial guesses can sometimes lead to different solutions. Disabling sometimes can aid in finding more non-local solutions for the orbitals.

GVB_GUESS_MIX

Similar to SCF_GUESS_MIX, it breaks alpha/beta symmetry for UPP by mixing the alpha HOMO and LUMO orbitals according to the user-defined fraction of LUMO to add the HOMO. 100 corresponds to a 1:1 ratio of HOMO and LUMO in the mixed orbitals.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-defined, $0 \le n \le 100$

RECOMMENDATION:

25 often works well to break symmetry without overly impeding convergence.

GVB_LOCAL

Sets the localization scheme used in the initial guess wavefunction.

TYPE:

INTEGER

DEFAULT:

2

Pipek-Mezey orbitals

OPTIONS:

0

No Localization

1

Boys localized orbitals

2

Pipek-Mezey orbitals

RECOMMENDATION:

Different initial guesses can sometimes lead to different solutions. It can be helpful to try both to ensure the global minimum has been found.

GVB_N_PAIRS

Alternative to CC_REST_OCC and CC_REST_VIR for setting active space size in GVB and valence coupled cluster methods.

TYPE:

INTEGER

DEFAULT:

PP active space (1 occ and 1 virt for each valence electron pair)

OPTIONS:

$n$

user-defined

RECOMMENDATION:

Use the default unless one wants to study a special active space. When using small active spaces, it is important to ensure that the proper orbitals are incorporated in the active space. If not, use the $reorder_mo feature to adjust the SCF orbitals appropriately.

GVB_OLD_UPP

Which unrestricted algorithm to use for GVB.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Use Unrestricted-in-Active Pairs

1

Use Unrestricted Implementation described in Ref. Beran:2005

RECOMMENDATION:

Only works for Unrestricted PP and no other GVB model.

GVB_ORB_CONV

The GVB-CC wavefunction is considered converged when the root-mean-square orbital gradient and orbital step sizes are less than $10^{-\ensuremath{\mathrm{GVB\_ ORB\_ CONV}}}$ . Adjust THRESH simultaneously.

TYPE:

INTEGER

DEFAULT:

5

OPTIONS:

$n$

User-defined

RECOMMENDATION:

Use 6 for PP(2) jobs or geometry optimizations. Tighter convergence (i.e. 7 or higher) cannot always be reliably achieved.

GVB_ORB_MAX_ITER

Controls the number of orbital iterations allowed in GVB-CC calculations. Some jobs, particularly unrestricted PP jobs can require 500–1000 iterations.

TYPE:

INTEGER

DEFAULT:

256

OPTIONS:

User-defined number of iterations.

RECOMMENDATION:

Default is typically adequate, but some jobs, particularly UPP jobs, can require 500–1000 iterations if converged tightly.

GVB_ORB_SCALE

Scales the default orbital step size by $n$ /1000.

TYPE:

INTEGER

DEFAULT:

1000

Corresponding to 100%

OPTIONS:

$n$

User-defined, 0–1000

RECOMMENDATION:

Default is usually fine, but for some stretched geometries it can help with convergence to use smaller values.

GVB_POWER

Coefficient for GVB_IP exchange type amplitude regularization to improve the convergence of the amplitude equations especially for spin-unrestricted amplitudes near dissociation. This is the leading coefficient for an amplitude dampening term included in the energy denominator: -( $c$ /10000) $(e^{t_{ij}^ p}-1)/(e^1-1)$

TYPE:

INTEGER

DEFAULT:

6

OPTIONS:

$p$

User-defined

RECOMMENDATION:

Should be decreased if unrestricted amplitudes do not converge or converge slowly at dissociation, and should be kept even valued.

GVB_PRINT

Controls the amount of information printed during a GVB-CC job.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-defined

RECOMMENDATION:

Should never need to go above 0 or 1.

GVB_REGULARIZE

Coefficient for GVB_IP exchange type amplitude regularization to improve the convergence of the amplitude equations especially for spin-unrestricted amplitudes near dissociation. This is the leading coefficient for an amplitude dampening term -( $c$ /10000) $(e^{t_{ij}^ p}-1)/(e^1-1)$

TYPE:

INTEGER

DEFAULT:

0 for restricted

1 for unrestricted

OPTIONS:

$c$

User-defined

RECOMMENDATION:

Should be increased if unrestricted amplitudes do not converge or converge slowly at dissociation. Set this to zero to remove all dynamically-valued amplitude regularization.

GVB_REORDER_1

Tells the code which two pairs to swap first

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-defined XXXYYY

RECOMMENDATION:

This is in the format of two 3-digit pair indices that tell the code to swap pair XXX with YYY, for example swapping pair 1 and 2 would get the input 001002. Must be specified in GVB_REORDER_PAIRS $\ge$ 1.

GVB_REORDER_2

Tells the code which two pairs to swap second

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-defined XXXYYY

RECOMMENDATION:

This is in the format of two 3-digit pair indices that tell the code to swap pair XXX with YYY, for example swapping pair 1 and 2 would get the input 001002. Must be specified in GVB_REORDER_PAIRS $\ge$ 2.

GVB_REORDER_3

Tells the code which two pairs to swap third

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-defined XXXYYY

RECOMMENDATION:

This is in the format of two 3-digit pair indices that tell the code to swap pair XXX with YYY, for example swapping pair 1 and 2 would get the input 001002. Must be specified in GVB_REORDER_PAIRS $\ge$ 3.

GVB_REORDER_4

Tells the code which two pairs to swap fourth

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-defined XXXYYY

RECOMMENDATION:

This is in the format of two 3-digit pair indices that tell the code to swap pair XXX with YYY, for example swapping pair 1 and 2 would get the input 001002. Must be specified in GVB_REORDER_PAIRS $\ge$ 4.

GVB_REORDER_5

Tells the code which two pairs to swap fifth

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-defined XXXYYY

RECOMMENDATION:

This is in the format of two 3-digit pair indices that tell the code to swap pair XXX with YYY, for example swapping pair 1 and 2 would get the input 001002. Must be specified in GVB_REORDER_PAIRS $\ge$ 5.

GVB_REORDER_PAIRS

Tells the code how many GVB pairs to switch around

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

$0 \le n \le 5$

RECOMMENDATION:

This allows for the user to change the order the active pairs are placed in after the orbitals are read in or are guessed using localization and the Sano procedure. Up to 5 sequential pair swaps can be made, but it is best to leave this alone.

GVB_RESTART

Restart a job from previously-converged GVB-CC orbitals.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

Useful when trying to converge to the same GVB solution at slightly different geometries, for example.

GVB_SHIFT

Value for a statically valued energy shift in the energy denominator used to solve the coupled cluster amplitude equations, $n$ /10000.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-defined

RECOMMENDATION:

Default is fine, can be used in lieu of the dynamically valued amplitude regularization if it does not aid convergence.

GVB_SYMFIX

Should GVB use a symmetry breaking fix

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

no symmetry breaking fix

1

symmetry breaking fix with virtual orbitals spanning the active space

2

symmetry breaking fix with virtual orbitals spanning the whole virtual space

RECOMMENDATION:

It is best to stick with type 1 to get a symmetry breaking correction with the best results coming from CORRELATION=NP and GVB_SYMFIX=1.

GVB_SYMPEN

Sets the pre-factor for the amplitude regularization term for the SB amplitudes

TYPE:

INTEGER

DEFAULT:

160

OPTIONS:

$\gamma$

User-defined

RECOMMENDATION:

Sets the pre-factor for the amplitude regularization term for the SB amplitudes: $-(\gamma /1000)(e^{(c*100)*t^2}-1)$ .

GVB_SYMSCA

Sets the weight for the amplitude regularization term for the SB amplitudes

TYPE:

INTEGER

DEFAULT:

125

OPTIONS:

$c$

User-defined

RECOMMENDATION:

Sets the weight for the amplitude regularization term for the SB amplitudes: $-(\gamma /1000)(e^{(c*100)*t^2}-1)$ .

GVB_TRUNC_OCC

Controls how many pairs’ occupied orbitals are truncated from the GVB active space

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-defined

RECOMMENDATION:

This allows for asymmetric GVB active spaces removing the $n$ lowest energy occupied orbitals from the GVB active space while leaving their paired virtual orbitals in the active space. Only the models including the SIP and DIP amplitudes (ie NP and 2P) benefit from this all other models this equivalent to just reducing the total number of pairs.

GVB_TRUNC_VIR

Controls how many pairs’ virtual orbitals are truncated from the GVB active space

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-defined

RECOMMENDATION:

This allows for asymmetric GVB active spaces removing the $n$ highest energy occupied orbitals from the GVB active space while leaving their paired virtual orbitals in the active space. Only the models including the SIP and DIP amplitudes (ie NP and 2P) benefit from this all other models this equivalent to just reducing the total number of pairs.

GVB_UNRESTRICTED

Controls restricted versus unrestricted PP jobs. Usually handled automatically.

TYPE:

LOGICAL

DEFAULT:

same value as UNRESTRICTED

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

Set this variable explicitly only to do a UPP job from an RHF or ROHF initial guess. Leave this variable alone and specify UNRESTRICTED=TRUE to access the new Unrestricted-in-Active-Pairs GVB code which can return an RHF or ROHF solution if used with GVB_DO_ROHF

HESS_AND_GRAD

Enables the evaluation of both analytical gradient and Hessian in a single job

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Evaluates both gradient and Hessian.

FALSE

Evaluates Hessian only.

RECOMMENDATION:

Use only in a frequency (and thus Hessian) evaluation.

HFPT_BASIS

Specifies the secondary basis in a HFPC/DFPC calculation.

TYPE:

STRING

DEFAULT:

None

OPTIONS:

None

RECOMMENDATION:

See reference for recommended basis set, functional, and grid pairings.

HFPT

Activates HFPC/DFPC calculation.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

Single-point energy only

RECOMMENDATION:

Use Dual-Basis to capture large-basis effects at smaller basis cost. See reference for recommended basis set, functional, and grid pairings.

HF_LR

Sets the fraction of Hartree-Fock exchange at r $_{12}$ = $\infty$ .

TYPE:

INTEGER

DEFAULT:

No default

OPTIONS:

$n$

Corresponding to HF_LR = $n/1000$

RECOMMENDATION:

None

HF_SR

Sets the fraction of Hartree-Fock exchange at r $_{12}$ =0.

TYPE:

INTEGER

DEFAULT:

No default

OPTIONS:

$n$

Corresponding to HF_SR = $n/1000$

RECOMMENDATION:

None

HIRSHFELD_READ

Switch to force reading in of isolated atomic densities.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Read in isolated atomic densities from previous Hirshfeld calculation from disk.

FALSE

Generate new isolated atomic densities.

RECOMMENDATION:

Use default unless system is large. Note, atoms should be in the same order with same basis set used as in the previous Hirshfeld calculation (although coordinates can change). The previous calculation should be run with the -save switch.

HIRSHFELD_SPHAVG

Controls whether atomic densities should be spherically averaged in pro-molecule.

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

Spherically average atomic densities.

FALSE

Do not spherically average.

RECOMMENDATION:

Use default.

HIRSHFELD

Controls running of Hirshfeld population analysis.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Calculate Hirshfeld populations.

FALSE

Do not calculate Hirshfeld populations.

RECOMMENDATION:

None

HIRSHITER_THRESH

Controls the convergence criterion of iterative Hirshfeld population analysis.

TYPE:

INTEGER

DEFAULT:

5

OPTIONS:

$\Delta$

Corresponding to the convergence criterion of $N/10000$ , in $e$ .

RECOMMENDATION:

Use the default, which is the value recommended in Ref. Bultinck:2007

HIRSHITER

Controls running of iterative Hirshfeld population analysis.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Calculate iterative Hirshfeld populations.

FALSE

Do not calculate iterative Hirshfeld populations.

RECOMMENDATION:

None

ICVICK

Specifies whether to perform cavity check

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

0

no cavity check, use only the outer cavity

1

cavity check, generating both the inner and outer cavities and compare.

RECOMMENDATION:

Consider turning off cavity check only if the molecule has a hole and if a star (outer) surface is expected.

IDERIV

Controls the order of derivatives that are evaluated analytically. The user is not normally required to specify a value, unless numerical derivatives are desired. The derivatives will be evaluated numerically if IDERIV is set lower than JOBTYPE requires.

TYPE:

INTEGER

DEFAULT:

Set to the order of derivative that JOBTYPE requires

OPTIONS:

2

Analytic second derivatives of the energy (Hessian)

1

Analytic first derivatives of the energy.

0

Analytic energies only.

RECOMMENDATION:

Usually set to the maximum possible for efficiency. Note that IDERIV will be set lower if analytic derivatives of the requested order are not available.

IGDEFIELD

Triggers the calculation of the electrostatic potential and/or the electric field at the positions of the MM charges.

TYPE:

INTEGER

DEFAULT:

UNDEFINED

OPTIONS:

O

Computes ESP.

1

Computes ESP and EFIELD.

2

Computes EFIELD.

RECOMMENDATION:

Must use this $rem when IGDESP is specified.

IGDESP

Controls evaluation of the electrostatic potential on a grid of points. If enabled, the output is in an ASCII file, plot.esp, in the format $x, y, z,$ esp for each point.

TYPE:

INTEGER

DEFAULT:

none no electrostatic potential evaluation

OPTIONS:

$-1$

read grid input via the $plots section of the input deck

$0$

Generate the ESP values at all nuclear positions.

+ $n$

read $n$ grid points in bohrs (!) from the ASCII file ESPGrid.

RECOMMENDATION:

None

IGNORE_LOW_FREQ

Low frequencies that should be treated as rotation can be ignored during

anharmonic correction calculation.

TYPE:

INTEGER

DEFAULT:

300

Corresponding to 300 cm $^{-1}$ .

OPTIONS:

$n$

Any mode with harmonic frequency less than $n$ will be ignored.

RECOMMENDATION:

Use default.

INCDFT_DENDIFF_THRESH

Sets the threshold for screening density matrix values in the IncDFT procedure.

TYPE:

INTEGER

DEFAULT:

SCF_CONVERGENCE + 3

OPTIONS:

$n$

Corresponding to a threshold of $10^{-n}$ .

RECOMMENDATION:

If the default value causes convergence problems, set this value higher to tighten the threshold.

INCDFT_DENDIFF_VARTHRESH

Sets the lower bound for the variable threshold for screening density matrix values in the IncDFT procedure. The threshold will begin at this value and then vary depending on the error in the current SCF iteration until the value specified by INCDFT_DENDIFF_THRESH is reached. This means this value must be set lower than INCDFT_DENDIFF_THRESH.

TYPE:

INTEGER

DEFAULT:

0

Variable threshold is not used.

OPTIONS:

$n$

Corresponding to a threshold of $10^{-n}$ .

RECOMMENDATION:

If the default value causes convergence problems, set this value higher to tighten accuracy. If this fails, set to 0 and use a static threshold.

INCDFT_GRIDDIFF_THRESH

Sets the threshold for screening functional values in the IncDFT procedure

TYPE:

INTEGER

DEFAULT:

SCF_CONVERGENCE + 3

OPTIONS:

$n$

Corresponding to a threshold of $10^{-n}$ .

RECOMMENDATION:

If the default value causes convergence problems, set this value higher to tighten the threshold.

INCDFT_GRIDDIFF_VARTHRESH

Sets the lower bound for the variable threshold for screening the functional values in the IncDFT procedure. The threshold will begin at this value and then vary depending on the error in the current SCF iteration until the value specified by INCDFT_GRIDDIFF_THRESH is reached. This means that this value must be set lower than INCDFT_GRIDDIFF_THRESH.

TYPE:

INTEGER

DEFAULT:

0

Variable threshold is not used.

OPTIONS:

$n$

Corresponding to a threshold of $10^{-n}$ .

RECOMMENDATION:

If the default value causes convergence problems, set this value higher to tighten accuracy. If this fails, set to 0 and use a static threshold.

INCDFT

Toggles the use of the IncDFT procedure for DFT energy calculations.

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

FALSE

Do not use IncDFT

TRUE

Use IncDFT

RECOMMENDATION:

Turning this option on can lead to faster SCF calculations, particularly towards the end of the SCF. Please note that for some systems use of this option may lead to convergence problems.

INCFOCK

Iteration number after which the incremental Fock matrix algorithm is initiated

TYPE:

INTEGER

DEFAULT:

1

Start INCFOCK after iteration number 1

OPTIONS:

User-defined (0 switches INCFOCK off)

RECOMMENDATION:

May be necessary to allow several iterations before switching on INCFOCK.

INTCAV

A flag to select the surface integration method.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Single center Lebedev integration.

1

Single center spherical polar integration.

RECOMMENDATION:

The Lebedev integration is by far the more efficient.

INTEGRALS_BUFFER

Controls the size of in-core integral storage buffer.

TYPE:

INTEGER

DEFAULT:

15

15 Megabytes.

OPTIONS:

User defined size.

RECOMMENDATION:

Use the default, or consult your systems administrator for hardware limits.

INTEGRAL_2E_OPR

Determines the two-electron operator.

TYPE:

INTEGER

DEFAULT:

-2

Coulomb Operator.

OPTIONS:

-1

Apply the CASE approximation.

-2

Coulomb Operator.

RECOMMENDATION:

Use default unless the CASE operator is desired.

INTRACULE

Controls whether intracule properties are calculated (see also the $intracule section).

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

No intracule properties.

TRUE

Evaluate intracule properties.

RECOMMENDATION:

None

IOPPRD

Specifies the choice of system operator form.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Symmetric form.

1

Non-symmetric form.

RECOMMENDATION:

The default uses more memory but is generally more efficient, we recommend its use unless there is shortage of memory available.

IP_STATES

Sets the number of ionized target states roots to find. By default, $\beta$ electron will be removed (see EOM_IP_BETA).

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any IP states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ ionized states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

IROTGR

Rotation of the cavity surface integration grid.

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

0

No rotation.

1

Rotate initial $xyz$ axes of the integration grid to coincide

with principal moments of nuclear inertia (relevant if ITRNGR=1)

2

Rotate initial $xyz$ axes of integration grid to coincide with

principal moments of nuclear charge (relevant if ITRNGR=2)

3

Rotate initial $xyz$ axes of the integration grid through user-specified

Euler angles as defined by Wilson, Decius, and Cross.

RECOMMENDATION:

The default is recommended unless the knowledgeable user has good reason otherwise.

ISHAPE

A flag to set the shape of the cavity surface.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

use the electronic iso-density surface.

1

use a spherical cavity surface.

RECOMMENDATION:

Use the default surface.

ISOTOPES

Specifies if non-default masses are to be used in the frequency calculation.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Use default masses only.

TRUE

Read isotope masses from $isotopes section.

RECOMMENDATION:

None

ITRNGR

Translation of the cavity surface integration grid.

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

0

No translation (i.e., center of the cavity at the origin

of the atomic coordinate system)

1

Translate to the center of nuclear mass.

2

Translate to the center of nuclear charge.

3

Translate to the midpoint of the outermost atoms.

4

Translate to midpoint of the outermost non-hydrogen atoms.

5

Translate to user-specified coordinates in Bohr.

6

Translate to user-specified coordinates in Angstroms.

RECOMMENDATION:

The default value is recommended unless the single-center integrations procedure fails.

JOBTYPE

Specifies the type of calculation.

TYPE:

STRING

DEFAULT:

SP

OPTIONS:

SP

Single point energy.

OPT

Geometry Minimization.

TS

Transition Structure Search.

FREQ

Frequency Calculation.

FORCE

Analytical Force calculation.

RPATH

Intrinsic Reaction Coordinate calculation.

NMR

NMR chemical shift calculation.

ISSC

Indirect nuclear spin–spin coupling calculation.

BSSE

BSSE calculation.

EDA

Energy decomposition analysis.

RECOMMENDATION:

Job dependent

KS_GAP_PRINT

Control printing of (generalized Kohn-Sham) HOMO-LUMO gap information.

TYPE:

Boolean

DEFAULT:

false

OPTIONS:

false

(default) do not print gap information

true

print gap information

RECOMMENDATION:

Use in conjunction with KS_GAP_UNIT if true.

KS_GAP_UNIT

Unit for KS_GAP_PRINT and FOA_FUNDGAP

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

(default) hartrees

1

eV

RECOMMENDATION:

none

LB94_BETA

Set the $\beta$ parameter of LB94 xc potential

TYPE:

INTEGER

DEFAULT:

500

OPTIONS:

$n$

Corresponding to $\beta = n/10000$ .

RECOMMENDATION:

Use default, i.e., $\beta =0.05$

LINEQ

Flag to select the method for solving the linear equations that determine the apparent point charges on the cavity surface.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

0

use LU decomposition in memory if space permits, else switch to LINEQ=2

1

use conjugate gradient iterations in memory if space permits, else use LINEQ=2

2

use conjugate gradient iterations with the system matrix stored externally on disk.

RECOMMENDATION:

The default should be sufficient in most cases.

LINK_ATOM_PROJECTION

Controls whether to perform a link-atom projection

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

Performs the projection

FALSE

No projection

RECOMMENDATION:

Necessary in a full QM/MM Hessian evaluation on a system with link atoms

LIN_K

Controls whether linear scaling evaluation of exact exchange (LinK) is used.

TYPE:

LOGICAL

DEFAULT:

Program chooses, switching on LinK whenever CFMM is used.

OPTIONS:

TRUE

Use LinK

FALSE

Do not use LinK

RECOMMENDATION:

Use for HF and hybrid DFT calculations with large numbers of atoms.

LOBA_THRESH

Specifies the thresholds to use for LOBA

TYPE:

INTEGER

DEFAULT:

6015

OPTIONS:

$aabb$

$aa$

specifies the threshold to use for localization

$bb$

specifies the threshold to use for occupation

Both are measured in %

RECOMMENDATION:

Decrease $bb$ to see the smaller contributions to orbitals. Values of $aa$ between 40 and 75 have been shown to given meaningful results.

LOBA

Specifies the methods to use for LOBA

TYPE:

INTEGER

DEFAULT:

00

OPTIONS:

$ab$

$a$

specifies the localization method

0 Perform Boys localization.

1 Perform PM localization.

2 Perform ER localization.

$b$

specifies the population analysis method

0 Do not perform LOBA. This is the default.

1 Use Mulliken population analysis.

2 Use Löwdin population analysis.

RECOMMENDATION:

Boys Localization is the fastest. ER will require an auxiliary basis set.

LOBA 12 provides a reasonable speed/accuracy compromise.

LOCAL_INTERP_ORDER

Controls the order of the B-spline

TYPE:

INTEGER

DEFAULT:

6

OPTIONS:

n, an integer

RECOMMENDATION:

The default value is sufficiently accurate

LOC_CIS_OV_SEPARATE

Decide whether or not to localized the “occupied” and “virtual” components of the localized diabatization function, i.e., whether to localize the electron attachments and detachments separately.

TYPE:

LOGICAL

DEFAULT:

FALSE

Do not separately localize electron attachments and detachments.

OPTIONS:

TRUE

RECOMMENDATION:

If one wants to use Boys localized diabatization for energy transfer (as opposed to electron transfer) , this is a necessary option. ER is more rigorous technique, and does not require this OV feature, but will be somewhat slower.

LOWDIN_POPULATION

Run a Löwdin population analysis instead of a Mulliken.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not calculate Löwdin Populations.

TRUE

Run Löwdin Population analyses instead of Mulliken.

RECOMMENDATION:

None

LRC_DFT

Controls the application of long-range-corrected DFT

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

(or 0) Do not apply long-range correction.

TRUE

(or 1) Use the long-range-corrected version of the requested functional.

RECOMMENDATION:

Long-range correction is available for any combination of Hartree-Fock, B88, and PBE exchange (along with any stand-alone correlation functional).

MAKE_CUBE_FILES

Requests generation of cube files for MOs, NTOs, or NBOs.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not generate cube files.

TRUE

Generate cube files for MOs and densities.

NTOS

Generate cube files for NTOs.

NBOS

Generate cube files for NBOs.

RECOMMENDATION:

None

MANY_BODY_INT

Perform a MBE calculation.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE

Perform a MBE calculation.

FALSE

Do not perform a MBE calculation.

RECOMMENDATION:

NONE

MAX_CIS_CYCLES

Maximum number of CIS iterative cycles allowed

TYPE:

INTEGER

DEFAULT:

30

OPTIONS:

$n$

User-defined number of cycles

RECOMMENDATION:

Default is usually sufficient.

MAX_CIS_SUBSPACE

Maximum number of subspace vectors allowed in the CIS iterations

TYPE:

INTEGER

DEFAULT:

As many as required to converge all roots

OPTIONS:

$n$

User-defined number of subspace vectors

RECOMMENDATION:

The default is usually appropriate, unless a large number of states are requested for a large molecule. The total memory required to store the subspace vectors is bounded above by $2nOV$ , where $O$ and $V$ represent the number of occupied and virtual orbitals, respectively. $n$ can be reduced to save memory, at the cost of a larger number of CIS iterations. Convergence may be impaired if $n$ is not much larger than $\ensuremath{\mathrm{CIS\_ N\_ ROOTS}}$ .

MAX_DIIS_CYCLES

The maximum number of DIIS iterations before switching to (geometric) direct minimization when SCF_ALGORITHM is DIIS_GDM or DIIS_DM. See also THRESH_DIIS_SWITCH.

TYPE:

INTEGER

DEFAULT:

50

OPTIONS:

1

Only a single Roothaan step before switching to (G)DM

$n$

$n$ DIIS iterations before switching to (G)DM.

RECOMMENDATION:

None

MAX_RCA_CYCLES

The maximum number of RCA iterations before switching to DIIS when SCF_ALGORITHM is RCA_DIIS.

TYPE:

INTEGER

DEFAULT:

50

OPTIONS:

N

N RCA iterations before switching to DIIS

RECOMMENDATION:

None

MAX_SCF_CYCLES

Controls the maximum number of SCF iterations permitted.

TYPE:

INTEGER

DEFAULT:

50

OPTIONS:

User-defined.

RECOMMENDATION:

Increase for slowly converging systems such as those containing transition metals.

MECP_METHODS

Determines which method to be used.

TYPE:

STRING

DEFAULT:

BRANCHING_PLANE

OPTIONS:

BRANCHING_PLANE

Use the branching-plane updating method.

MECP_DIRECT

Use the direct method.

PENALTY_FUNCTION

Use the penalty-constrained method.

RECOMMENDATION:

The direct method is stable for small molecules or molecules with high symmetries, but the branching-plane updating method is more efficient for larger molecules. However, the latter does not work if the two states have different symmetries. If using branching plane updating method, GEOM_OPT_COORDS must be set to 0 in the $rem section (i.e., this algorithm is available in Cartesian coordinates only). The penalty-constrained method converges slowly and is suggested only when the other methods do not work.

MECP_OPT

Determines whether we are doing MECP optimizations.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Do MECP optimizations.

FALSE

Don’t do MECP optimizations.

RECOMMENDATION:

None.

MECP_PROJ_HESS

Determines whether to project out the coupling vector from the Hessian when using branching plane updating method.

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

FALSE

RECOMMENDATION:

Use Default.

MECP_STATE1

Determines the first state for crossing.

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

None

OPTIONS:

[ $i$ , $j$ ]

find the $j$ th excited state with the total spin of $i$ ; $j=0$ means the SCF ground state.

RECOMMENDATION:

$i$ is ignored for restricted calculations; for unrestricted calculations, $i$ can only be 0 or 1.

MECP_STATE2

Determines the second state for crossing.

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

None

OPTIONS:

[ $i$ , $j$ ]

find the $j$ th excited state with the total spin of $i$ ; $j=0$ means the SCF ground state.

RECOMMENDATION:

$i$ is ignored for restricted calculations; for unrestricted calculations, $i$ can only be 0 or 1.

MEM_STATIC

Sets the memory for individual program modules

TYPE:

INTEGER

DEFAULT:

64

corresponding to 64 Mb

OPTIONS:

$n$

User-defined number of megabytes.

RECOMMENDATION:

At least $150(N^2 + N)D$ of MEM_STATIC is required ( $N$ : number of basis functions, $D$ : size of a double precision storage, usually 8). Because a number of matrices with $N^2$ size also need to be stored, 32–160 Mb of additional MEM_STATIC is needed.

MEM_STATIC

Sets the memory for Fortran AO integral calculation and transformation modules.

TYPE:

INTEGER

DEFAULT:

64

corresponding to 64 Mb.

OPTIONS:

$n$

User-defined number of megabytes.

RECOMMENDATION:

For direct and semi-direct MP2 calculations, this must exceed OVN + requirements for AO integral evaluation (32–160 Mb), as discussed above.

MEM_TOTAL

Sets the total memory available to Q-Chem

TYPE:

INTEGER

DEFAULT:

2000

2 Gb

OPTIONS:

$n$

User-defined number of megabytes

RECOMMENDATION:

The minimum memory requirement of RI-CIS(D) is approximately MEM_STATIC + max $(3SVXD, 3X^2D)$ ( $S$ : number of excited states, $X$ : number of auxiliary basis functions, $D$ : size of a double precision storage, usually 8). However, because RI-CIS(D) uses a batching scheme for efficient evaluations of electron repulsion integrals, specifying more memory will significantly speed up the calculation. Put as much memory as possible if you are not sure what to use, but never put any more than what is available. The minimum memory requirement of SOS-CIS(D) and SOS-CIS(D $_0$ ) is approximately MEM_STATIC + $20 X^2 D$ . SOS-CIS(D $_0$ ) gradient calculation becomes more efficient when $30 X^2 D$ more memory space is given. Like in RI-CIS(D), put as much memory as possible if you are not sure what to use. The actual memory size used in these calculations will be printed out in the output file to give a guide about the required memory.

MEM_TOTAL

Sets the total memory available to Q-Chem, in megabytes.

TYPE:

INTEGER

DEFAULT:

2000

(2 Gb)

OPTIONS:

$n$

User-defined number of megabytes.

RECOMMENDATION:

Use default, or set to the physical memory of your machine. Note that if more than 1GB is specified for a CCMAN job, the memory is allocated as follows

12%

MEM_STATIC

50%

CC_MEMORY

35%

Other memory requirements:

METECO

Sets the threshold criteria for discarding shell-pairs.

TYPE:

INTEGER

DEFAULT:

2

Discard shell-pairs below $10^{-\mathrm{THRESH}}$ .

OPTIONS:

1

Discard shell-pairs four orders of magnitude below machine precision.

2

Discard shell-pairs below 10 $^{-\mathrm{THRESH}}$ .

RECOMMENDATION:

Use default.

METHOD

Specifies the level of theory.

TYPE:

STRING

DEFAULT:

No default

OPTIONS:

HF

Exact (Hartree-Fock).

RECOMMENDATION:

Use HF for Hartree-Fock calculations.

METHOD

Specifies the level of theory, either DFT or wavefunction-based.

TYPE:

STRING

DEFAULT:

HF

No correlation, Hartree-Fock exchange

OPTIONS:

MP2

Sections 5.2 and 5.3

RI-MP2

Section 5.5

Local_MP2

Section 5.4

RILMP2

Section 5.5.1

ATTMP2

Section 5.6.1

ATTRIMP2

Section 5.6.1

ZAPT2

A more efficient restricted open-shell MP2 method [230].

MP3

Section 5.2

MP4SDQ

Section 5.2

MP4

Section 5.2

CCD

Section 5.7

CCD(2)

Section 5.8

CCSD

Section 5.7

CCSD(T)

Section 5.8

CCSD(2)

Section 5.8

CCSD(fT)

Section 5.8.3

CCSD(dT)

Section 5.8.3

QCISD

Section 5.7

QCISD(T)

Section 5.8

OD

Section 5.7

OD(T)

Section 5.8

OD(2)

Section 5.8

VOD

Section 5.9

VOD(2)

Section 5.9

QCCD

Section 5.7

QCCD(T)

QCCD(2)

VQCCD

Section 5.9

RECOMMENDATION:

Consult the literature for guidance.

MGC_AMODEL

Choice of approximate cluster model.

TYPE:

INTEGER

DEFAULT:

Determines

how the CC equations are approximated:

OPTIONS:

0%

Local Active-Space Amplitude iterations.

(pre-calculate GVB orbitals with

your method of choice (RPP is good)).

7%

Optimize-Orbitals using the VOD 2-step solver.

(Experimental only use with MGC_AMPS = 2, 24 ,246)

8%

Traditional Coupled Cluster up to CCSDTQPH.

9%

MR-CC version of the Pair-Models. (Experimental)

RECOMMENDATION:

MGC_AMPS

Choice of Amplitude Truncation

TYPE:

INTEGER

DEFAULT:

none

OPTIONS:

2 $\leq$ n $\leq$ 123456, a sorted list of integers for every amplitude

which will be iterated. Choose 1234 for PQ and 123456 for PH

RECOMMENDATION:

MGC_LOCALINTER

Pair filter on an intermediate.

TYPE:

BOOL

DEFAULT:

FALSE

OPTIONS:

Any nonzero value enforces the pair constraint on intermediates,

significantly reducing computational cost. Not recommended for $\leq$ 2 pair locality

RECOMMENDATION:

MGC_LOCALINTS

Pair filter on an integrals.

TYPE:

BOOL

DEFAULT:

FALSE

OPTIONS:

Enforces a pair filter on the 2-electron integrals, significantly

reducing computational cost. Generally useful. for more than 1 pair locality.

RECOMMENDATION:

MGC_NLPAIRS

Number of local pairs on an amplitude.

TYPE:

INTEGER

DEFAULT:

none

OPTIONS:

Must be greater than 1, which corresponds to the PP model. 2 for PQ, and 3 for PH.

RECOMMENDATION:

MGEMM_THRESH

Sets MGEMM threshold to determine the separation between “large” and “small” matrix elements. A larger threshold value will result in a value closer to the single-precision result. Note that the desired factor should be multiplied by 10000 to ensure an integer value.

TYPE:

INTEGER

DEFAULT:

10000 (corresponds to 1

OPTIONS:

n

user-defined threshold

RECOMMENDATION:

For small molecules and basis sets up to triple- $\zeta$ , the default value suffices to not deviate too much from the double-precision values. Care should be taken to reduce this number for larger molecules and also larger basis-sets.

MM_CHARGES

Requests the calculation of multipole-derived charges (MDCs).

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Calculates the MDCs and also the traceless form of the multipole moments

RECOMMENDATION:

Set to TRUE if MDCs or the traceless form of the multipole moments are desired. The calculation does not take long.

MM_SUBTRACTIVE

Specifies whether a subtractive scheme is used in the $E_{Coul}$ , Eq. eq:ECoul, portion of the calculation.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Only pairs that are not 1-2, 1-3, or 1-4 pairs are used.

TRUE

All pairs are calculated, and then the pairs that are double counted (1-2, 1-3, and 1-4) are subtracted out.

RECOMMENDATION:

When running QM/MM or MM calculations there is not recommendation. When running a QM/MM Ewald calculation the value must be set to TRUE.

MODEL_SYSTEM_CHARGE

Specifies the QM subsystem charge if different from the $molecule section.

TYPE:

INTEGER

DEFAULT:

NONE

OPTIONS:

$n$

The charge of the QM subsystem.

RECOMMENDATION:

This option only needs to be used if the QM subsystem (model system) has a charge that is different from the total system charge.

MODEL_SYSTEM_MULT

Specifies the QM subsystem multiplicity if different from the $molecule section.

TYPE:

INTEGER

DEFAULT:

NONE

OPTIONS:

$n$

The multiplicity of the QM subsystem.

RECOMMENDATION:

This option only needs to be used if the QM subsystem (model system) has a multiplicity that is different from the total system multiplicity. ONIOM calculations must be closed shell.

MODE_COUPLING

Number of modes coupling in the third and fourth derivatives calculation.

TYPE:

INTEGER

DEFAULT:

2

for two modes coupling.

OPTIONS:

$n$

for $n$ modes coupling, Maximum value is 4.

RECOMMENDATION:

Use default.

MOLDEN_FORMAT

Requests a MolDen-formatted input file containing information from a Q-Chem job.

TYPE:

LOGICAL

DEFAULT:

False

OPTIONS:

True

Append MolDen input file at the end of the Q-Chem output file.

RECOMMENDATION:

None.

MOM_PRINT

Switches printing on within the MOM procedure.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Printing is turned off

TRUE

Printing is turned on.

RECOMMENDATION:

None

MOM_START

Determines when MOM is switched on to stabilize DIIS iterations.

TYPE:

INTEGER

DEFAULT:

0 (FALSE)

OPTIONS:

0 (FALSE)

MOM is not used

$n$

MOM begins on cycle $n$ .

RECOMMENDATION:

Set to 1 if preservation of initial orbitals is desired. If MOM is to be used to aid convergence, an SCF without MOM should be run to determine when the SCF starts oscillating. MOM should be set to start just before the oscillations.

MOPROP_CONV_1ST

Sets the convergence criteria for CPSCF and 1st order TDSCF.

TYPE:

INTEGER

DEFAULT:

6

OPTIONS:

$n<10$

Convergence threshold set to $10^{-n}$ .

RECOMMENDATION:

None

MOPROP_CONV_2ND

Sets the convergence criterion for second-order TDSCF.

TYPE:

INTEGER

DEFAULT:

6

OPTIONS:

$n<10$

Convergence threshold set to $10^{-n}$ .

RECOMMENDATION:

None

MOPROP_DIIS_DIM_SS

Specified the DIIS subspace dimension.

TYPE:

INTEGER

DEFAULT:

20

OPTIONS:

0

No DIIS.

$n$

Use a subspace of dimension $n$ .

RECOMMENDATION:

None

MOPROP_DIIS

Controls the use of Pulay’s DIIS in solving the CPSCF equations.

TYPE:

INTEGER

DEFAULT:

5

OPTIONS:

0

Turn off DIIS.

5

Turn on DIIS.

RECOMMENDATION:

None

MOPROP_ISSC_PRINT_REDUCED

Specifies whether the isotope-independent reduced coupling tensor $\mathbf{K}$ should be printed in addition to the isotope-dependent $\mathbf{J}$ -tensor when calculating indirect nuclear spin–spin couplings.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not print $\mathbf{K}$ .

TRUE

Print $\mathbf{K}$ .

RECOMMENDATION:

None

MOPROP_ISSC_SKIP_DSO

Specifies whether to skip the calculation of the diamagnetic spin–orbit contribution to the indirect nuclear spin–spin coupling tensor.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Calculate diamagnetic spin–orbit contribution.

TRUE

Skip diamagnetic spin–orbit contribution.

RECOMMENDATION:

None

MOPROP_ISSC_SKIP_FC

Specifies whether to skip the calculation of the Fermi contact contribution to the indirect nuclear spin–spin coupling tensor.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Calculate Fermi contact contribution.

TRUE

Skip Fermi contact contribution.

RECOMMENDATION:

None

MOPROP_ISSC_SKIP_PSO

Specifies whether to skip the calculation of the paramagnetic spin–orbit contribution to the indirect nuclear spin–spin coupling tensor.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Calculate paramagnetic spin–orbit contribution.

TRUE

Skip paramagnetic spin–orbit contribution.

RECOMMENDATION:

None

MOPROP_ISSC_SKIP_SD

Specifies whether to skip the calculation of the spin–dipole contribution to the indirect nuclear spin–spin coupling tensor.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Calculate spin–dipole contribution.

TRUE

Skip spin–dipole contribution.

RECOMMENDATION:

None

MOPROP_MAXITER_1ST

The maximum number of iterations for CPSCF and first-order TDSCF.

TYPE:

INTEGER

DEFAULT:

50

OPTIONS:

$n$

Set maximum number of iterations to $n$ .

RECOMMENDATION:

Use default.

MOPROP_MAXITER_2ND

The maximum number of iterations for second-order TDSCF.

TYPE:

INTEGER

DEFAULT:

50

OPTIONS:

$n$

Set maximum number of iterations to $n$ .

RECOMMENDATION:

Use default.

MOPROP_PERTNUM

Set the number of perturbed densities that will to be treated together.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

All at once.

$n$

Treat the perturbed densities batch-wise.

RECOMMENDATION:

Use default. For large systems, limiting this number may be required to avoid memory exhaustion.

MOPROP

Specifies the job for mopropman.

TYPE:

INTEGER

DEFAULT:

0

Do not run mopropman.

OPTIONS:

1

NMR chemical shielding tensors.

2

Static polarizability.

3

Indirect nuclear spin–spin coupling tensors.

100

Dynamic polarizability.

101

First hyperpolarizability.

102

First hyperpolarizability, reading First order results from disk.

103

First hyperpolarizability using Wigner’s $(2n+1)$ rule.

104

First hyperpolarizability using Wigner’s $(2n+1)$ rule, reading

first order results from disk.

RECOMMENDATION:

None

MRXC_CLASS_THRESH_MULT

Controls the of smoothness precision

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

im, an integer

RECOMMENDATION:

a prefactor in the threshold for mrxc error control: im*10.0 $^{-io}$

MRXC_CLASS_THRESH_ORDER

Controls the of smoothness precision

TYPE:

INTEGER

DEFAULT:

6

OPTIONS:

io, an integer

RECOMMENDATION:

The exponent in the threshold of the mrxc error control: im*10.0 $^{-io}$

MRXC

Controls the use of MRXC.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not use MRXC

1

Use MRXC in the evaluation of the XC part

RECOMMENDATION:

MRXC is very efficient for medium and large molecules, especially when medium and large basis sets are used.

MULTIPOLE_ORDER

Determines highest order of multipole moments to print if wavefunction analysis requested.

TYPE:

INTEGER

DEFAULT:

4

OPTIONS:

$n$

Calculate moments to $n$ th order.

RECOMMENDATION:

Use default unless higher multipoles are required.

NBO

Controls the use of the NBO package.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not invoke the NBO package.

1

Do invoke the NBO package, for the ground state.

2

Invoke the NBO package for the ground state, and also each

CIS, RPA, or TDDFT excited state.

RECOMMENDATION:

None

NL_CORRELATION

Specifies a non-local correlation functional that includes non-empirical dispersion.

TYPE:

STRING

DEFAULT:

None

No non-local correlation.

OPTIONS:

None

No non-local correlation

vdW-DF-04

the non-local part of vdW-DF-04

vdW-DF-10

the nonlocal part of vdW-DF-10 (aka vdW-DF2)

VV09

the nonlocal part of VV09

VV10

the nonlocal part of VV10

RECOMMENDATION:

Do not forget to add the LSDA correlation (PW92 is recommended) when using vdW-DF-04, vdW-DF-10, or VV09. VV10 should be used with PBE correlation. Choose exchange functionals carefully: HF, rPW86, revPBE, and some of the LRC exchange functionals are among the recommended choices.

NL_GRID

Specifies the grid to use for non-local correlation.

TYPE:

INTEGER

DEFAULT:

1

SG-1 grid

OPTIONS:

Same as for XC_GRID

RECOMMENDATION:

Use default unless computational cost becomes prohibitive, in which case SG-0 may be used. XC_GRID should generally be finer than NL_GRID.

NL_VV_B

Sets the parameter $b$ in VV10. This parameter controls the short range behavior of the nonlocal correlation energy.

TYPE:

INTEGER

DEFAULT:

No default

OPTIONS:

$n$

Corresponding to $b = n/100$

RECOMMENDATION:

The optimal value depends strongly on the exchange functional used. $b = 5.9$ is recommended for rPW86. See further details in Ref. [135].

NL_VV_C

Sets the parameter $C$ in VV09 and VV10. This parameter is fitted to asymptotic van der Waals $C_6$ coefficients.

TYPE:

INTEGER

DEFAULT:

89

for VV09

No default

for VV10

OPTIONS:

$n$

Corresponding to $C = n/10000$

RECOMMENDATION:

$C = 0.0093$ is recommended when a semilocal exchange functional is used. $C = 0.0089$ is recommended when a long-range corrected (LRC) hybrid functional is used. See further details in Ref. [135].

NOCI_PRINT

Specify the debug print level of NOCI

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

RECOMMENDATION:

Increase this for more debug information

NPTLEB

The number of points used in the Lebedev grid for the single-center surface integration. (Only relevant if INTCAV=0).

TYPE:

INTEGER

DEFAULT:

1202

OPTIONS:

Valid choices are:

6, 18, 26, 38, 50, 86, 110, 146, 170, 194, 302, 350, 434, 590, 770,

974, 1202, 1454, 1730, 2030, 2354, 2702, 3074, 3470, 3890, 4334,

4802, or 5294.

RECOMMENDATION:

The default value has been found adequate to obtain the energy to within 0.1 kcal/mol for solutes the size of mono-substituted benzenes.

NPTTHE, NPTPHI

The number of ( $\theta$ , $\phi$ ) points used for single-centered surface integration (relevant only if INTCAV=1).

TYPE:

INTEGER

DEFAULT:

8,16

OPTIONS:

$\theta$ , $\phi$ specifying the number of points.

RECOMMENDATION:

These should be multiples of 2 and 4 respectively, to provide symmetry sufficient for all Abelian point groups. Defaults are too small for all but the tiniest and simplest solutes.

NTO_PAIRS

Controls the writing of hole/particle NTO pairs for excited state.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$N$

Write $N$ NTO pairs per excited state.

RECOMMENDATION:

If activated ( $N > 0$ ), a minimum of two NTO pairs will be printed for each state. Increase the value of $N$ if additional NTOs are desired.

NVO_LIN_CONVERGENCE

Target error factor in the preconditioned conjugate gradient solver of the single-excitation amplitude equations.

TYPE:

INTEGER

DEFAULT:

3

OPTIONS:

$n$

User–defined number.

RECOMMENDATION:

Solution of the single-excitation amplitude equations is considered converged if the maximum residual is less than $10^{-n}$ multiplied by the current DIIS error. For the ARS correction, $n$ is automatically set to 1 since the locally-projected DIIS error is normally several orders of magnitude smaller than the full DIIS error.

NVO_LIN_MAX_ITE

Maximum number of iterations in the preconditioned conjugate gradient solver of the single-excitation amplitude equations.

TYPE:

INTEGER

DEFAULT:

30

OPTIONS:

$n$

User–defined number of iterations.

RECOMMENDATION:

None.

NVO_METHOD

Sets method to be used to converge solution of the single-excitation amplitude equations.

TYPE:

INTEGER

DEFAULT:

9

OPTIONS:

$n$

User–defined number.

RECOMMENDATION:

Experimental option. Use default.

NVO_TRUNCATE_DIST

Specifies which atomic blocks of the Fock matrix are used to construct the preconditioner.

TYPE:

INTEGER

DEFAULT:

-1

OPTIONS:

$n>0$

If distance between a pair of atoms is more than $n$ angstroms

do not include the atomic block.

-2

Do not use distance threshold, use NVO_TRUNCATE_PRECOND instead.

-1

Include all blocks.

0

Include diagonal blocks only.

RECOMMENDATION:

This option does not affect the final result. However, it affects the rate of the PCG algorithm convergence. For small systems use default.

NVO_TRUNCATE_PRECOND

Specifies which atomic blocks of the Fock matrix are used to construct the preconditioner. This variable is used only if NVO_TRUNCATE_DIST is set to $-2$ .

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

$n$

If the maximum element in an atomic block is less than $10^{-n}$ do not include

the block.

RECOMMENDATION:

Use default. Increasing $n$ improves convergence of the PCG algorithm but overall may slow down calculations.

NVO_UVV_MAXPWR

Controls convergence of the Taylor series when calculating the $U_{vv}$ block from the single-excitation amplitudes. If the series is not converged at the $n$ th term, more expensive direct inversion is used to calculate the $U_{vv}$ block.

TYPE:

INTEGER

DEFAULT:

10

OPTIONS:

$n$

User–defined number.

RECOMMENDATION:

None.

NVO_UVV_PRECISION

Controls convergence of the Taylor series when calculating the $U_{vv}$ block from the single-excitation amplitudes. Series is considered converged when the maximum element of the term is less than $10^{-n}$ .

TYPE:

INTEGER

DEFAULT:

11

OPTIONS:

$n$

User–defined number.

RECOMMENDATION:

NVO_UVV_PRECISION must be the same as or larger than THRESH.

N_FROZEN_CORE

Controls the number of frozen core orbitals

TYPE:

INTEGER

DEFAULT:

0

No frozen core orbitals

OPTIONS:

FC

Frozen core approximation

$n$

Freeze $n$ core orbitals

RECOMMENDATION:

There is no computational advantage to using frozen core for CIS, and analytical derivatives are only available when no orbitals are frozen. It is helpful when calculating CIS(D) corrections (see Sec. 6.6).

N_FROZEN_CORE

Sets the number of frozen core orbitals in a post-Hartree–Fock calculation.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

FC

Frozen Core approximation (all core orbitals frozen).

$n$

Freeze $n$ core orbitals.

RECOMMENDATION:

While the default is not to freeze orbitals, MP2 calculations are more efficient with frozen core orbitals. Use FC if possible.

N_FROZEN_VIRTUAL

Controls the number of frozen virtual orbitals.

TYPE:

INTEGER

DEFAULT:

0

No frozen virtual orbitals

OPTIONS:

$n$

Freeze $n$ virtual orbitals

RECOMMENDATION:

There is no computational advantage to using frozen virtuals for CIS, and analytical derivatives are only available when no orbitals are frozen.

N_FROZEN_VIRTUAL

Sets the number of frozen virtual orbitals in a post-Hartree–Fock calculation.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

Freeze $n$ virtual orbitals.

RECOMMENDATION:

None

N_I_SERIES

Sets summation limit for series expansion evaluation of $i_ n(x)$ .

TYPE:

INTEGER

DEFAULT:

40

OPTIONS:

$n>0$

RECOMMENDATION:

Lower values speed up the calculation, but may affect accuracy.

N_J_SERIES

Sets summation limit for series expansion evaluation of $j_ n(x)$ .

TYPE:

INTEGER

DEFAULT:

40

OPTIONS:

$n>0$

RECOMMENDATION:

Lower values speed up the calculation, but may affect accuracy.

N_SOL

Specifies number of atoms included in the Hessian

TYPE:

INTEGER

DEFAULT:

No default

OPTIONS:

User defined

RECOMMENDATION:

None

N_WIG_SERIES

Sets summation limit for Wigner integrals.

TYPE:

INTEGER

DEFAULT:

10

OPTIONS:

$n<100$

RECOMMENDATION:

Increase $n$ for greater accuracy.

OCCUPATIONS

Activates pFON calculation.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Integer occupation numbers

1

Not yet implemented

2

Pseudo-fractional occupation numbers (pFON)

RECOMMENDATION:

Use pFON to improve convergence for small-gap systems.

OMEGA2

Sets the Coulomb attenuation parameter for the long-range component.

TYPE:

INTEGER

DEFAULT:

No default

OPTIONS:

$n$

Corresponding to $\omega 2 = n/1000$ , in units of bohr $^{-1}$

RECOMMENDATION:

None

OMEGA

Sets the Coulomb attenuation parameter $\omega$ .

TYPE:

INTEGER

DEFAULT:

No default

OPTIONS:

$n$

Corresponding to $\omega = n/1000$ , in units of bohr $^{-1}$

RECOMMENDATION:

None

OMEGA

Sets the Coulomb attenuation parameter for the short-range component.

TYPE:

INTEGER

DEFAULT:

No default

OPTIONS:

$n$

Corresponding to $\omega = n/1000$ , in units of bohr $^{-1}$

RECOMMENDATION:

None

PAO_ALGORITHM

Algorithm used to optimize polarized atomic orbitals (see PAO_METHOD)

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Use efficient (and riskier) strategy to converge PAOs.

1

Use conservative (and slower) strategy to converge PAOs.

RECOMMENDATION:

None

PAO_METHOD

Controls evaluation of polarized atomic orbitals (PAOs).

TYPE:

STRING

DEFAULT:

EPAO

For local MP2 calculations Otherwise no default.

OPTIONS:

PAO

Perform PAO-SCF instead of conventional SCF.

EPAO

Obtain EPAO’s after a conventional SCF.

RECOMMENDATION:

None

PAO_METHOD

Controls the type of PAO calculations requested.

TYPE:

STRING

DEFAULT:

EPAO

For local MP2, EPAOs are chosen by default.

OPTIONS:

EPAO

Find EPAOs by minimizing delocalization function.

PAO

Do SCF in a molecule-optimized minimal basis.

RECOMMENDATION:

None

PARI_K

Controls the use of the PARI-K approximation in the construction of the exchange matrix

TYPE:

LOGICAL

DEFAULT:

FALSE

Do not use PARI-K.

OPTIONS:

TRUE

Use PARI-K.

RECOMMENDATION:

Use for basis sets aug-cc-pVTZ and larger.

PBHT_ANALYSIS

Controls whether overlap analysis of electronic excitations is performed.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not perform overlap analysis

TRUE

Perform overlap analysis

RECOMMENDATION:

None

PBHT_FINE

Increases accuracy of overlap analysis

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

TRUE

Increase accuracy of overlap analysis

RECOMMENDATION:

None

PHESS

Controls whether partial Hessian calculations are performed.

TYPE:

INTEGER

DEFAULT:

0

Full Hessian calculation

OPTIONS:

0

Full Hessian calculation

1

Partial Hessian calculation

2

Vibrational subsystem analysis (massless)

3

Vibrational subsystem analysis (weighted)

RECOMMENDATION:

None

PH_FAST

Lowers integral cutoff in partial Hessian calculation is performed.

TYPE:

LOGICAL

DEFAULT:

FALSE

Use default cutoffs

OPTIONS:

TRUE

Lower integral cutoffs

RECOMMENDATION:

None

PIMC_ACCEPT_RATE

Acceptance rate for MC/PIMC simulations when Cartesian or normal-mode displacements are utilized.

TYPE:

INTEGER

DEFAULT:

None

OPTIONS:

$0 < n < 100$

User-specified rate, given as a whole-number percentage.

RECOMMENDATION:

Choose acceptance rate to maximize sampling efficiency, which is typically signified by the mean-square displacement (printed in the job output). Note that the maximum displacement is adjusted during the warmup run to achieve roughly this acceptance rate.

PIMC_MCMAX

Number of Monte Carlo steps to sample.

TYPE:

INTEGER

DEFAULT:

None.

OPTIONS:

User-specified number of steps to sample.

RECOMMENDATION:

This variable dictates the statistical convergence of MC/PIMC simulations. Recommend setting to at least 100000 for converged simulations.

PIMC_MOVETYPE

Selects the type of displacements used in MC/PIMC simulations.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Cartesian displacements of all beads, with occasional (1%) center-of-mass moves.

1

Normal-mode displacements of all modes, with occasional (1%) center-of-mass moves.

2

Levy flights without center-of-mass moves.

RECOMMENDATION:

Except for classical sampling (MC) or small bead-number quantum sampling (PIMC), Levy flights should be utilized. For Cartesian and normal-mode moves, the maximum displacement is adjusted during the warmup run to the desired acceptance rate (controlled by PIMC_ACCEPT_RATE). For Levy flights, the acceptance is solely controlled by PIMC_SNIP_LENGTH.

PIMC_NBEADSPERATOM

Number of path integral time slices (“beads”) used on each atom of a PIMC simulation.

TYPE:

INTEGER

DEFAULT:

None.

OPTIONS:

1

Perform classical Boltzmann sampling.

$>$ 1

Perform quantum-mechanical path integral sampling.

RECOMMENDATION:

This variable controls the inherent convergence of the path integral simulation. The 1-bead limit is purely classical sampling; the infinite-bead limit is exact quantum mechanical sampling. Using 32 beads is reasonably converged for room-temperature simulations of molecular systems.

PIMC_SNIP_LENGTH

Number of “beads” to use in the Levy flight movement of the ring polymer.

TYPE:

INTEGER

DEFAULT:

None

OPTIONS:

$3 \leq n \leq \mbox{{\small PIMC\_ NBEADSPERATOM}}$

User-specified length of snippet.

RECOMMENDATION:

Choose the snip length to maximize sampling efficiency. The efficiency can be estimated by the mean-square displacement between configurations, printed at the end of the output file. This efficiency will typically, however, be a trade-off between the mean-square displacement (length of statistical correlations) and the number of beads moved. Only the moved beads require recomputing the potential, i.e., a call to Q-Chem for the electronic energy. (Note that the endpoints of the snippet remain fixed during a single move, so $n-2$ beads are actually moved for a snip length of $n$ . For 1 or 2 beads in the simulation, Cartesian moves should be used instead.)

PIMC_TEMP

Temperature, in Kelvin (K), of path integral simulations.

TYPE:

INTEGER

DEFAULT:

None.

OPTIONS:

User-specified number of Kelvin for PIMC or classical MC simulations.

RECOMMENDATION:

None.

PIMC_WARMUP_MCMAX

Number of Monte Carlo steps to sample during an equilibration period of MC/PIMC simulations.

TYPE:

INTEGER

DEFAULT:

None.

OPTIONS:

User-specified number of steps to sample.

RECOMMENDATION:

Use this variable to equilibrate the molecule/ring polymer before collecting production statistics. Usually a short run of roughly 10% of PIMC_MCMAX is sufficient.

PLOT_SPIN_DENSITY

Requests the generation of spin densities, $\rho _\alpha$ and $\rho _\beta$ .

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not generate spin density cube files.

TRUE

Generate spin density cube files.

RECOMMENDATION:

Set to TRUE if spin densities are desired in addition to total densities. Requires that MAKE_CUBE_FILES be set to TRUE as well, and that one or more total densities is requested in the $plots input section. The corresponding spin densities will then be generated also.

POP_MULLIKEN

Controls running of Mulliken population analysis.

TYPE:

LOGICAL/INTEGER

DEFAULT:

TRUE

(or 1)

OPTIONS:

FALSE

(or 0) Do not calculate Mulliken Population.

TRUE

(or 1) Calculate Mulliken population

2

Also calculate shell populations for each occupied orbital.

$-1$

Calculate Mulliken charges for both the ground state and any CIS,

RPA, or TDDFT excited states.

RECOMMENDATION:

Leave as TRUE, unless excited-state charges are desired. Mulliken analysis is a trivial additional calculation, for ground or excited states.

PRINT_CORE_CHARACTER

Determines the print level for the CORE_CHARACTER option.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

No additional output is printed.

1

Prints core characters of occupied MOs.

2

Print level 1, plus prints the core character of AOs.

RECOMMENDATION:

Use default, unless you are uncertain about what the core character is.

PRINT_DIST_MATRIX

Controls the printing of the inter-atomic distance matrix

TYPE:

INTEGER

DEFAULT:

15

OPTIONS:

0

Turns off the printing of the distance matrix

$n$

Prints the distance matrix if the number of atoms in the molecule

is less than or equal to $n$ .

RECOMMENDATION:

Use default unless distances are required for large systems

PRINT_GENERAL_BASIS

Controls print out of built in basis sets in input format

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Print out standard basis set information

FALSE

Do not print out standard basis set information

RECOMMENDATION:

Useful for modification of standard basis sets.

PRINT_ORBITALS

Prints orbital coefficients with atom labels in analysis part of output.

TYPE:

INTEGER/LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not print any orbitals.

TRUE

Prints occupied orbitals plus 5 virtuals.

NVIRT

Number of virtuals to print.

RECOMMENDATION:

Use TRUE unless more virtuals are desired.

PRINT_RADII_GYRE

Controls printing of MO centroids and radii of gyration.

TYPE:

LOGICAL/INTEGER

DEFAULT:

FALSE

OPTIONS:

TRUE

(or 1) Print the centroid and radius of gyration for each occupied MO and each density.

2

Print centroids and radii of gyration for the virtual MOs as well.

FALSE

(or 0) Do not calculate these quantities.

RECOMMENDATION:

None

PROJ_TRANSROT

Removes translational and rotational drift during AIMD trajectories.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not apply translation/rotation corrections.

TRUE

Apply translation/rotation corrections.

RECOMMENDATION:

When computing spectra (see AIMD_NUCL_DACF_POINTS, for example), this option can be utilized to remove artificial, contaminating peaks stemming from translational and/or rotational motion. Recommend setting to TRUE for all dynamics-based spectral simulations.

PSEUDO_CANONICAL

When SCF_ALGORITHM = DM, this controls the way the initial step, and steps after subspace resets are taken.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Use Roothaan steps when (re)initializing

TRUE

Use a steepest descent step when (re)initializing

RECOMMENDATION:

The default is usually more efficient, but choosing TRUE sometimes avoids problems with orbital reordering.

PURECART

INTEGER

TYPE:

Controls the use of pure (spherical harmonic) or Cartesian angular forms

DEFAULT:

2111

Cartesian $h$ -functions and pure $g,f,d$ functions

OPTIONS:

$hgfd$

Use 1 for pure and 2 for Cartesian.

RECOMMENDATION:

This is pre-defined for all standard basis sets

QMMM_CHARGES

Controls the printing of QM charges to file.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Writes a charges.dat file with the Mulliken charges from the QM region.

FALSE

No file written.

RECOMMENDATION:

Use default unless running calculations with Charmm where charges on the QM region need to be saved.

QMMM_FULL_HESSIAN

Trigger the evaluation of the full QM/MM Hessian.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Evaluates full Hessian.

FALSE

Hessian for QM-QM block only.

RECOMMENDATION:

None

QMMM_PRINT

Controls the amount of output printed from a QM/MM job.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Limit molecule, point charge, and analysis printing.

FALSE

Normal printing.

RECOMMENDATION:

Use default unless running calculations with Charmm.

QM_MM_INTERFACE

Enables internal QM/MM calculations.

TYPE:

STRING

DEFAULT:

NONE

OPTIONS:

MM

Molecular mechanics calculation (i.e., no QM region)

ONIOM

QM/MM calculation using two-layer mechanical embedding

JANUS

QM/MM calculation using electronic embedding

RECOMMENDATION:

The ONIOM model and Janus models are described above. Choosing MM leads to no electronic structure calculation. However, when using MM, one still needs to define the $rem variables BASIS and EXCHANGE in order for Q-Chem to proceed smoothly.

QM_MM

Turns on the Q-Chem/Charmm interface.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Do QM/MM calculation through the Q-Chem/Charmm interface.

FALSE

Turn this feature off.

RECOMMENDATION:

Use default unless running calculations with Charmm.

RADSPH

Sphere radius used to specify the cavity surface (Only relevant for ISHAPE=1).

TYPE:

FLOAT

DEFAULT:

Half the distance between the outermost atoms plus 1.4 Angstroms.

OPTIONS:

Real number specifying the radius in bohr (if positive) or in Angstroms (if negative).

RECOMMENDATION:

Make sure that the cavity radius is larger than the length of the molecule.

RAS_ACT_DIFF

Sets the number of alpha vs. beta electrons

TYPE:

Integer

DEFAULT:

None

OPTIONS:

n

user defined integer

RECOMMENDATION:

Set to 1 for an odd number of electrons or a cation, -1 for an anion. Only works with RASCI2.

RAS_ACT_OCC

Sets the number of occupied orbitals to enter the RAS active space.

TYPE:

Integer

DEFAULT:

None

OPTIONS:

n

user defined integer

RECOMMENDATION:

None. Only works with RASCI2

RAS_ACT_ORB

Sets the user-selected active orbitals (RAS2 orbitals).

TYPE:

INTEGER ARRAY

DEFAULT:

From RAS_OCC+1 to RAS_OCC+RAS_ACT

OPTIONS:

$[i,j,k...]$

The number of orbitals must be equal to the RAS_ACT variable

RECOMMENDATION:

None. Only works with RASCI.

RAS_ACT_VIR

Sets the number of virtual orbitals to enter the RAS active space.

TYPE:

Integer

DEFAULT:

None

OPTIONS:

n

user defined integer

RECOMMENDATION:

None. Only works with RASCI2.

RAS_ACT

Sets the number of orbitals in RAS2 (active orbitals).

TYPE:

INTEGER

DEFAULT:

None

OPTIONS:

$n$

User-defined integer, $n>0$

RECOMMENDATION:

None. Only works with RASCI.

RAS_AMPL_PRINT

Defines the absolute threshold ( $\times 10^2$ ) for the CI amplitudes to be printed.

TYPE:

INTEGER

DEFAULT:

10

0.1 minimum absolute amplitude

OPTIONS:

$n$

User-defined integer, $n\geq 0$

RECOMMENDATION:

None. Only works with RASCI.

RAS_DO_HOLE

Controls the presence of hole excitations in the RAS-CI wavefunction.

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

Include hole configurations (RAS1 to RAS2 excitations)

FALSE

Do not include hole configurations

RECOMMENDATION:

None. Only works with RASCI.

RAS_DO_PART

Controls the presence of particle excitations in the RAS-CI wavefunction.

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

Include particle configurations (RAS2 to RAS3 excitations)

FALSE

Do not include particle configurations

RECOMMENDATION:

None. Only works with RASCI.

RAS_ELEC

Sets the number of electrons in RAS2 (active electrons).

TYPE:

INTEGER

DEFAULT:

None

OPTIONS:

$n$

User-defined integer, $n>0$

RECOMMENDATION:

None. Only works with RASCI.

RAS_GUESS_CS

Controls the number of closed shell guess configurations in RAS-CI.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

Imposes to start with $n$ closed shell guesses

RECOMMENDATION:

Only relevant for the computation of singlet states. Only works with RASCI.

RAS_NATORB_STATE

Allows to save the natural orbitals of a RAS-CI computed state.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$i$

Saves the natural orbitals for the $i$ -th state

RECOMMENDATION:

None. Only works with RASCI.

RAS_NATORB

Controls the computation of the natural orbital occupancies.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Compute natural orbital occupancies for all states

FALSE

Do not compute natural orbital occupancies

RECOMMENDATION:

None. Only works with RASCI.

RAS_N_ROOTS

Sets the number of RAS-CI roots to be computed.

TYPE:

INTEGER

DEFAULT:

None

OPTIONS:

$n$

$n>0$ Compute $n$ RAS-CI states

RECOMMENDATION:

None. Only works with RASCI2

RAS_OCC

Sets the number of orbitals in RAS1

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

User-defined integer, $n>0$

RECOMMENDATION:

These are the initial doubly occupied orbitals (RAS1) before including $hole$ type of excitations. The RAS1 space starts from the lowest orbital up to RAS_OCC, i.e. no frozen orbitals option available yet. Only works with RASCI.

RAS_ROOTS

Sets the number of RAS-CI roots to be computed.

TYPE:

INTEGER

DEFAULT:

None

OPTIONS:

$n$

$n>0$ Compute $n$ RAS-CI states

RECOMMENDATION:

None. Only works with RASCI.

RAS_SPIN_MULT

Specifies the spin multiplicity of the roots to be computed

TYPE:

INTEGER

DEFAULT:

1

Singlet states

OPTIONS:

0

Compute any spin multiplicity

$2n+1$

User-defined integer, $n\geq 0$

RECOMMENDATION:

Only for RASCI, which at present only allows for the computation of systems with an even number of electrons. Thus, RAS_SPIN_MULT only can take odd values.

RCA_PRINT

Controls the output from RCA SCF optimizations.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

No print out

1

RCA summary information

2

Level 1 plus RCA coefficients

3

Level 2 plus RCA iteration details

RECOMMENDATION:

None

RC_R0

Determines the parameter in the Gaussian weight function used to smooth the density at the nuclei.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Corresponds the traditional delta function spin and charge densities

$n$

corresponding to $n\times 10^{-3}$ a.u.

RECOMMENDATION:

We recommend value of 250 for a typical spit valence basis. For basis sets with increased flexibility in the nuclear vicinity the smaller values of $r_0$ also yield adequate spin density.

RHOISO

Value of the electronic iso-density contour used to specify the cavity surface. (Only relevant for ISHAPE = 0).

TYPE:

FLOAT

DEFAULT:

0.001

OPTIONS:

Real number specifying the density in electrons/bohr $^3$ .

RECOMMENDATION:

The default value is optimal for most situations. Increasing the value produces a smaller cavity which ordinarily increases the magnitude of the solvation energy.

RI_J

Toggles the use of the RI algorithm to compute J.

TYPE:

LOGICAL

DEFAULT:

FALSE

RI will not be used to compute J.

OPTIONS:

TRUE

Turn on RI for J.

RECOMMENDATION:

For large (especially 1D and 2D) molecules the approximation may yield significant improvements in Fock evaluation time when used with ARI.

RI_K

Toggles the use of the RI algorithm to compute K.

TYPE:

LOGICAL

DEFAULT:

FALSE

RI will not be used to compute K.

OPTIONS:

TRUE

Turn on RI for K.

RECOMMENDATION:

For large (especially 1D and 2D) molecules the approximation may yield significant improvements in Fock evaluation time when used with ARI.

ROKS_LEVEL_SHIFT

Introduce a level shift of N/100 Hartree to aid convergence.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

No shift

N

level shift of N/100 Hartree.

RECOMMENDATION:

Use in cases of problematic convergence.

ROKS

Controls whether ROKS calculation will be performed.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

ROKS is not performed.

TRUE

ROKS will be performed.

RECOMMENDATION:

Set to TRUE if ROKS calculation is desired. You should also set UNRESTRICTED=TRUE

ROTTHE ROTPHI ROTCHI

Euler angles ( $\theta$ , $\phi$ , $\chi$ ) in degrees for user-specified rotation of the cavity surface. (relevant if IROTGR=3)

TYPE:

FLOAT

DEFAULT:

0,0,0

OPTIONS:

$\theta$ , $\phi$ , $\chi$ in degrees

RECOMMENDATION:

None.

RPATH_COORDS

Determines which coordinate system to use in the IRC search.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Use mass-weighted coordinates.

1

Use Cartesian coordinates.

2

Use Z-matrix coordinates.

RECOMMENDATION:

Use default.

RPATH_DIRECTION

Determines the direction of the eigen mode to follow. This will not usually be known prior to the Hessian diagonalization.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

1

Descend in the positive direction of the eigen mode.

-1

Descend in the negative direction of the eigen mode.

RECOMMENDATION:

It is usually not possible to determine in which direction to go a priori, and therefore both directions will need to be considered.

RPATH_MAX_CYCLES

Specifies the maximum number of points to find on the reaction path.

TYPE:

INTEGER

DEFAULT:

20

OPTIONS:

$n$

User-defined number of cycles.

RECOMMENDATION:

Use more points if the minimum is desired, but not reached using the default.

RPATH_MAX_STEPSIZE

Specifies the maximum step size to be taken (in thousandths of a.u.).

TYPE:

INTEGER

DEFAULT:

150

corresponding to a step size of 0.15 a.u..

OPTIONS:

$n$

Step size = $n$ /1000.

RECOMMENDATION:

None.

RPATH_PRINT

Specifies the print output level.

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

$n$

RECOMMENDATION:

Use default, little additional information is printed at higher levels. Most of the output arises from the multiple single point calculations that are performed along the reaction pathway.

RPATH_TOL_DISPLACEMENT

Specifies the convergence threshold for the step. If a step size is chosen by the algorithm that is smaller than this, the path is deemed to have reached the minimum.

TYPE:

INTEGER

DEFAULT:

5000

Corresponding to 0.005 a.u.

OPTIONS:

$n$

User-defined. Tolerance = $n$ /1000000.

RECOMMENDATION:

Use default. Note that this option only controls the threshold for ending the RPATH job and does nothing to the intermediate steps of the calculation. A smaller value will provide reaction paths that end closer to the true minimum. Use of smaller values without adjusting RPATH_MAX_STEPSIZE, however, can lead to oscillations about the minimum.

RPA

Do an RPA calculation in addition to a CIS or TDDFT/TDA calculation

TYPE:

LOGICAL/INTEGER

DEFAULT:

False

OPTIONS:

False

Do not do an RPA calculation

True

Do an RPA calculation.

2

Do an RPA calculation without running CIS or TDDFT/TDA first

RECOMMENDATION:

None

SAVE_LAST_GPX

Save last $\ensuremath{\mathbf{G}}\left[\ensuremath{\mathbf{P}}^{\ensuremath{\mathrm{x}}}\right]$ when calculating dynamic polarizabilities in order to call mopropman in a second run with MOPROP = 102.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

False

1

True

RECOMMENDATION:

None

SCALE_NUCLEAR_CHARGE

Scales charge of each nuclei by a certain value. The nuclear repulsion energy is calculated for the unscaled nuclear charges.

TYPE:

INTEGER

DEFAULT:

0 no scaling.

OPTIONS:

n a total positive charge of (1+n/100)e is added to the molecule.

RECOMMENDATION:

NONE

SCF_ALGORITHM

Algorithm used for converging the SCF.

TYPE:

STRING

DEFAULT:

DIIS

Pulay DIIS.

OPTIONS:

DIIS

Pulay DIIS.

DM

Direct minimizer.

DIIS_DM

Uses DIIS initially, switching to direct minimizer for later iterations

(See THRESH_DIIS_SWITCH, MAX_DIIS_CYCLES).

DIIS_GDM

Use DIIS and then later switch to geometric direct minimization

(See THRESH_DIIS_SWITCH, MAX_DIIS_CYCLES).

GDM

Geometric Direct Minimization.

RCA

Relaxed constraint algorithm

RCA_DIIS

Use RCA initially, switching to DIIS for later iterations (see

THRESH_RCA_SWITCH and MAX_RCA_CYCLES described

later in this chapter)

ROOTHAAN

Roothaan repeated diagonalization.

RECOMMENDATION:

Use DIIS unless performing a restricted open-shell calculation, in which case GDM is recommended. If DIIS fails to find a reasonable approximate solution in the initial iterations, RCA_DIIS is the recommended fallback option. If DIIS approaches the correct solution but fails to finally converge, DIIS_GDM is the recommended fallback.

SCF_CONVERGENCE

SCF is considered converged when the wavefunction error is less that $10^{-\mathrm{SCF\_ CONVERGENCE}}$ . Adjust the value of THRESH at the same time. Note that in Q-Chem 3.0 the DIIS error is measured by the maximum error rather than the RMS error as in previous versions.

TYPE:

INTEGER

DEFAULT:

5

For single point energy calculations.

8

For geometry optimizations and vibrational analysis.

8

For SSG calculations, see Chapter 5.

OPTIONS:

User-defined

RECOMMENDATION:

Tighter criteria for geometry optimization and vibration analysis. Larger values provide more significant figures, at greater computational cost.

SCF_FINAL_PRINT

Controls level of output from SCF procedure to Q-Chem output file at the end of the SCF.

TYPE:

INTEGER

DEFAULT:

0

No extra print out.

OPTIONS:

0

No extra print out.

1

Orbital energies and break-down of SCF energy.

2

Level 1 plus MOs and density matrices.

3

Level 2 plus Fock and density matrices.

RECOMMENDATION:

The break-down of energies is often useful (level 1).

SCF_GUESS_ALWAYS

Switch to force the regeneration of a new initial guess for each series of SCF iterations (for use in geometry optimization).

TYPE:

LOGICAL

DEFAULT:

False

OPTIONS:

False

Do not generate a new guess for each series of SCF iterations in an

optimization; use MOs from the previous SCF calculation for the guess,

if available.

True

Generate a new guess for each series of SCF iterations in a geometry

optimization.

RECOMMENDATION:

Use default unless SCF convergence issues arise

SCF_GUESS_MIX

Controls mixing of LUMO and HOMO to break symmetry in the initial guess. For unrestricted jobs, the mixing is performed only for the alpha orbitals.

TYPE:

INTEGER

DEFAULT:

0 (FALSE)

Do not mix HOMO and LUMO in SCF guess.

OPTIONS:

0 (FALSE)

Do not mix HOMO and LUMO in SCF guess.

1 (TRUE)

Add 10% of LUMO to HOMO to break symmetry.

$n$

Add $n\times 10\%$ of LUMO to HOMO ( $0<n<10$ ).

RECOMMENDATION:

When performing unrestricted calculations on molecules with an even number of electrons, it is often necessary to break alpha/beta symmetry in the initial guess with this option, or by specifying input for $occupied.

SCF_GUESS_PRINT

Controls printing of guess MOs, Fock and density matrices.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not print guesses.

SAD

1

Atomic density matrices and molecular matrix.

2

Level 1 plus density matrices.

CORE and GWH

1

No extra output.

2

Level 1 plus Fock and density matrices and, MO coefficients and

eigenvalues.

READ

1

No extra output

2

Level 1 plus density matrices, MO coefficients and eigenvalues.

RECOMMENDATION:

None

SCF_GUESS

Specifies the initial guess procedure to use for the SCF.

TYPE:

STRING

DEFAULT:

SAD

Superposition of atomic density (available only with standard basis sets)

GWH

For ROHF where a set of orbitals are required.

FRAGMO

For a fragment MO calculation

OPTIONS:

CORE

Diagonalize core Hamiltonian

SAD

Superposition of atomic density

GWH

Apply generalized Wolfsberg-Helmholtz approximation

READ

Read previous MOs from disk

FRAGMO

Superimposing converged fragment MOs

RECOMMENDATION:

SAD guess for standard basis sets. For general basis sets, it is best to use the BASIS2 $rem. Alternatively, try the GWH or core Hamiltonian guess. For ROHF it can be useful to READ guesses from an SCF calculation on the corresponding cation or anion. Note that because the density is made spherical, this may favor an undesired state for atomic systems, especially transition metals. Use FRAGMO in a fragment MO calculation.

SCF_MINFIND_INCREASEFACTOR

Controls how the height of the penalty function changes when repeatedly trapped at the same solution

TYPE:

INTEGER

DEFAULT:

10100 meaning 1.01

OPTIONS:

$abcde$

corresponding to $a.bcde$

RECOMMENDATION:

If the algorithm converges to a solution which corresponds to a previously located solution, increase both the normalization N and the width lambda of the penalty function there. Then do a restart.

SCF_MINFIND_INITLAMBDA

Control the initial width of the penalty function.

TYPE:

INTEGER

DEFAULT:

02000 meaning 2.000

OPTIONS:

$abcde$

corresponding to $ab.cde$

RECOMMENDATION:

The initial inverse-width (i.e., the inverse-variance) of the Gaussian to place to fill solution’s well. Measured in electrons $^(-1)$ . Increasing this will repeatedly converging on the same solution.

SCF_MINFIND_INITNORM

Control the initial height of the penalty function.

TYPE:

INTEGER

DEFAULT:

01000 meaning 1.000

OPTIONS:

$abcde$ corresponding to $ab.cde$

RECOMMENDATION:

The initial normalization of the Gaussian to place to fill a well. Measured in Hartrees.

SCF_MINFIND_MIXENERGY

Specify the active energy range when doing Active mixing

TYPE:

INTEGER

DEFAULT:

00200 meaning 00.200

OPTIONS:

$abcde$ corresponding to $ab.cde$

RECOMMENDATION:

The standard deviation of the Gaussian distribution used to select the orbitals for mixing (centered on the Fermi level). Measured in Hartree. To find less-excited solutions, decrease this value

SCF_MINFIND_MIXMETHOD

Specify how to select orbitals for random mixing

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Random mixing: select from any orbital to any orbital.

1

Active mixing: select based on energy, decaying with distance from the Fermi level.

2

Active Alpha space mixing: select based on energy, decaying with distance from the

Fermi level only in the alpha space.

RECOMMENDATION:

Random mixing will often find very high energy solutions. If lower energy solutions are desired, use 1 or 2.

SCF_MINFIND_NRANDOMMIXES

Control how many random mixes to do to generate new orbitals

TYPE:

INTEGER

DEFAULT:

10

OPTIONS:

$n$

Perform $n$ random mixes.

RECOMMENDATION:

This is the number of occupied/virtual pairs to attempt to mix, per separate density (i.e., for unrestricted calculations both alpha and beta space will get this many rotations). If this is negative then only mix the highest 25% occupied and lowest 25% virtuals.

SCF_MINFIND_RANDOMMIXING

Control how to choose new orbitals after locating a solution

TYPE:

INTEGER

DEFAULT:

00200 meaning .02 radians

OPTIONS:

$abcde$ corresponding to $a.bcde$ radians

RECOMMENDATION:

After locating an SCF solution, the orbitals are mixed randomly to move to a new position in orbital space. For each occupied and virtual orbital pair picked at random and rotate between them by a random angle between 0 and this. If this is negative then use exactly this number, e.g., $-15708$ will almost exactly swap orbitals. Any number $<-15708$ will cause the orbitals to be swapped exactly.

SCF_MINFIND_READDISTTHRESH

The distance threshold at which to consider two solutions the same

TYPE:

INTEGER

DEFAULT:

00100 meaning 0.1

OPTIONS:

$abcde$ corresponding to $ab.cde$

RECOMMENDATION:

The threshold to regard a minimum as the same as a read in minimum. Measured in electrons. If two minima are closer together than this, reduce the threshold to distinguish them.

SCF_MINFIND_RESTARTSTEPS

Restart with new orbitals if no minima have been found within this many steps

TYPE:

INTEGER

DEFAULT:

300

OPTIONS:

$n$

Restart after $n$ steps.

RECOMMENDATION:

If the SCF calculation spends many steps not finding a solution, lowering this number may speed up solution-finding. If the system converges to solutions very slowly, then this number may need to be raised.

SCF_MINFIND_RUNCORR

Run post-SCF correlated methods on multiple SCF solutions

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

If this is set $>0$ , then run correlation methods for all found SCF solutions.

RECOMMENDATION:

Post-HF correlation methods should function correctly with excited SCF solutions, but their convergence is often much more difficult owing to intruder states.

SCF_MINFIND_WELLTHRESH

Specify what SCF_MINFIND believes is the basin of a solution

TYPE:

INTEGER

DEFAULT:

5

OPTIONS:

$n$ for a threshold of $10^{-n}$

RECOMMENDATION:

When the DIIS error is less than $10^{-n}$ , penalties are switched off to see whether it has converged to a new solution.

SCF_PRINT_FRGM

Controls the output of Q-Chem jobs on isolated fragments.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

The output is printed to the parent job output file.

FALSE

The output is not printed.

RECOMMENDATION:

Use TRUE if details about isolated fragments are important.

SCF_PRINT

Controls level of output from SCF procedure to Q-Chem output file.

TYPE:

INTEGER

DEFAULT:

0

Minimal, concise, useful and necessary output.

OPTIONS:

0

Minimal, concise, useful and necessary output.

1

Level 0 plus component breakdown of SCF electronic energy.

2

Level 1 plus density, Fock and MO matrices on each cycle.

3

Level 2 plus two-electron Fock matrix components (Coulomb, HF exchange

and DFT exchange-correlation matrices) on each cycle.

RECOMMENDATION:

Proceed with care; can result in extremely large output files at level 2 or higher. These levels are primarily for program debugging.

SCF_READMINIMA

Read in solutions from a previous SCF Metadynamics calculation

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

Read in $n$ previous solutions and attempt to locate them all.

$-n$

Read in $n$ previous solutions, but only attempt to locate solution $n$ .

RECOMMENDATION:

This may not actually locate all solutions required and will probably locate others too. The SCF will also stop when the number of solutions specified in SCF_SAVEMINIMA are found. Solutions from other geometries may also be read in and used as starting orbitals. If a solution is found and matches one that is read in within SCF_MINFIND_READDISTTHRESH, its orbitals are saved in that position for any future calculations. The algorithm works by restarting from the orbitals and density of a the minimum it is attempting to find. After 10 failed restarts (defined by SCF_MINFIND_RESTARTSTEPS), it moves to another previous minimum and attempts to locate that instead. If there are no minima to find, the restart does random mixing (with 10 times the normal random mixing parameter).

SCF_SAVEMINIMA

Turn on SCF Metadynamics and specify how many solutions to locate.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not use SCF Metadynamics

$n$

Attempt to find $n$ distinct SCF solutions.

RECOMMENDATION:

Perform SCF Orbital metadynamics and attempt to locate $n$ different SCF solutions. Note that these may not all be minima. Many saddle points are often located. The last one located will be the one used in any post-SCF treatments. In systems where there are infinite point groups, this procedure cannot currently distinguish between spatial rotations of different densities, so will likely converge on these multiply.

SET_QUADRATIC

Determines whether to include full quadratic reponse contributions for TDDFT.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Include full quadratic reponse contributions for TDDFT.

FALSE

Use pseudo-wavefunction approach.

RECOMMENDATION:

The pseudo-wavefunction approach is usually accurate enough. Consult Refs. Zhang:2015 and Ou:2015 for additional guidance.

SET_STATE_DERIV

Sets the excited state index for analytical gradient calculation for geometry optimizations and vibrational analysis with SOS-CIS(D $_0$ )

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

Select the $n$ th state.

RECOMMENDATION:

Check to see that the states do no change order during an optimization. For closed-shell systems, either CIS_SINGLETS or CIS_TRIPLETS must be set to false.

SFX_AMP_OCC_A

Defines a customer amplitude guess vector in SF-XCIS method

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

builds a guess amplitude with an $\alpha$ -hole in the $n$ th orbital (requires SFX_AMP_VIR_B).

RECOMMENDATION:

Only use when default guess is not satisfactory

SFX_AMP_VIR_B

Defines a customer amplitude guess vector in SF-XCIS method

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$

builds a guess amplitude with a $\beta$ -particle in the $n$ th orbital (requires SFX_AMP_OCC_A).

RECOMMENDATION:

Only use when default guess is not satisfactory

SF_STATES

Sets the number of spin-flip target states roots to find.

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0

Do not look for any spin-flip states.

OPTIONS:

$[i,j,k\ldots ]$

Find $i$ SF states in the first irrep, $j$ states in the second irrep etc.

RECOMMENDATION:

None

SKIP_CIS_RPA

Skips the solution of the CIS, RPA, TDA or TDDFT equations for wavefunction analysis.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE / FALSE

RECOMMENDATION:

Set to true to speed up the generation of plot data if the same calculation has been run previously with the scratch files saved.

SOLVENT_METHOD

Sets the preferred solvent method.

TYPE:

STRING

DEFAULT:

0

OPTIONS:

0

Do not use a solvation model.

ONSAGER

Use the Kirkwood-Onsager model (Section 11.2.1).

PCM

Use an apparent surface charge, polarizable continuum model

(Section 11.2.2).

ISOSVP

Use the iso-density implementation of the SS(V)PE model

(Section 11.2.5).

COSMO

Use COSMO (similar to C-PCM but with an outlying charge

correction [599, 600]; see Section 11.2.6).

SM8

Use version 8 of the Cramer-Truhlar SM $x$ model (Section 11.2.7.1).

SM12

Use version 12 of the SM $x$ model (Section 11.2.7.2).

CHEM_SOL

Use the Langevin Dipoles model (Section 11.2.8).

RECOMMENDATION:

Consult the literature. PCM is a collective name for a family of models and additional input options may be required in this case, in order to fully specify the model. (See Section 11.2.2.) Several versions of SM12 are available as well, as discussed in Section 11.2.7.2.

SOS_FACTOR

Controls the strength of the opposite-spin component of PT2 correlation energy.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

n

Corresponding to $c_{os} = n/1000000$ in Eq. (4.65).

RECOMMENDATION:

NONE

SOS_UFACTOR

Sets the scaling parameter $c_ U$

TYPE:

INTEGER

DEFAULT:

151

For SOS-CIS(D), corresponding to 1.51

140

For SOS-CIS(D $_0$ ), corresponding to 1.40

OPTIONS:

$n$

$c_ U = n / 100$

RECOMMENDATION:

Use the default

SPIN_FLIP_XCIS

Do a SF-XCIS calculation

TYPE:

LOGICAL

DEFAULT:

False

OPTIONS:

False

Do not do an SF-XCIS calculation

True

Do an SF-XCIS calculation (requires ROHF triplet ground state).

RECOMMENDATION:

None

SPIN_FLIP

Selects whether to perform a standard excited state calculation, or a spin-flip calculation. Spin multiplicity should be set to 3 for systems with an even number of electrons, and 4 for systems with an odd number of electrons.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

None

SRC_DFT

Selects form of the short-range corrected functional

TYPE:

INTEGER

DEFAULT:

No default

OPTIONS:

1

SRC1 functional

2

SRC2 functional

RECOMMENDATION:

None

SSG

Controls the calculation of the SSG wavefunction.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

Do not compute the SSG wavefunction

1

Do compute the SSG wavefunction

RECOMMENDATION:

See also the UNRESTRICTED and DIIS_SUBSPACE_SIZE $rem variables.

SSS_FACTOR

Controls the strength of the same-spin component of PT2 correlation energy.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

n

Corresponding to $c_{ss} = n/1000000$ in Eq. (4.65).

RECOMMENDATION:

NONE

STABILITY_ANALYSIS

Performs stability analysis for a HF or DFT solution.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Perform stability analysis.

FALSE

Do not perform stability analysis.

RECOMMENDATION:

Set to TRUE when a HF or DFT solution is suspected to be unstable.

STATE_ANALYSIS

Activates excited state analyses.

TYPE:

LOGICAL

DEFAULT:

FALSE (no excited state analyses)

OPTIONS:

TRUE, FALSE

RECOMMENDATION:

Set to TRUE if excited state analysis is required, but also if plots of densities or orbitals are needed. For details see section 10.2.7.

STS_ACCEPTOR

Define the acceptor molecular fragment.

TYPE:

STRING

DEFAULT:

0

No acceptor fragment is defined.

OPTIONS:

$i$ - $j$

Acceptor fragment is in the $i$ th atom to the $j$ th atom.

RECOMMENDATION:

Note no space between the hyphen and the numbers $i$ and $j$ .

STS_DONOR

Define the donor fragment.

TYPE:

STRING

DEFAULT:

0

No donor fragment is defined.

OPTIONS:

$i$ - $j$

Donor fragment is in the $i$ th atom to the $j$ th atom.

RECOMMENDATION:

Note no space between the hyphen and the numbers $i$ and $j$ .

STS_FCD

Control the calculation of FCD for ET couplings.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not perform an FCD calculation.

TRUE

Include an FCD calculation.

RECOMMENDATION:

None

STS_FED

Control the calculation of FED for EET couplings.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not perform a FED calculation.

TRUE

Include a FED calculation.

RECOMMENDATION:

None

STS_FSD

Control the calculation of FSD for EET couplings.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not perform a FSD calculation.

TRUE

Include a FSD calculation.

RECOMMENDATION:

For RCIS triplets, FSD and FED are equivalent. FSD will be automatically switched off and perform a FED calculation.

STS_GMH

Control the calculation of GMH for ET couplings.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not perform a GMH calculation.

TRUE

Include a GMH calculation.

RECOMMENDATION:

When set to true computes Mulliken-Hush electronic couplings. It yields the generalized Mulliken-Hush couplings as well as the transition dipole moments for each pair of excited states and for each excited state with the ground state.

STS_MOM

Control calculation of the transition moments between excited states in the CIS and TDDFT calculations (including SF variants).

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not calculate state-to-state transition moments.

TRUE

Do calculate state-to-state transition moments.

RECOMMENDATION:

When set to true requests the state-to-state dipole transition moments for all pairs of excited states and for each excited state with the ground state.

SVP_CAVITY_CONV

Determines the convergence value of the iterative iso-density cavity procedure.

TYPE:

INTEGER

DEFAULT:

10

OPTIONS:

$n$ Convergence threshold set to $10^{-n}$ .

RECOMMENDATION:

The default value unless convergence problems arise.

SVP_CHARGE_CONV

Determines the convergence value for the charges on the cavity. When the change in charges fall below this value, if the electron density is converged, then the calculation is considered converged.

TYPE:

INTEGER

DEFAULT:

7

OPTIONS:

$n$ Convergence threshold set to $10^{-n}$ .

RECOMMENDATION:

The default value unless convergence problems arise.

SVP_GUESS

Specifies how and if the solvation module will use a given guess for the charges and cavity points.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

No guessing.

1

Read a guess from a previous Q-Chem solvation computation.

2

Use a guess specified by the $svpirf section from the input

RECOMMENDATION:

It is helpful to also set SCF_GUESS to READ when using a guess from a previous Q-Chem run.

SVP_MEMORY

Specifies the amount of memory for use by the solvation module.

TYPE:

INTEGER

DEFAULT:

125

OPTIONS:

$n$ corresponds to the amount of memory in MB.

RECOMMENDATION:

The default should be fine for medium size molecules with the default Lebedev grid, only increase if needed.

SVP_PATH

Specifies whether to run a gas phase computation prior to performing the solvation procedure.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

runs a gas-phase calculation and after

convergence runs the SS(V)PE computation.

1

does not run a gas-phase calculation.

RECOMMENDATION:

Running the gas-phase calculation provides a good guess to start the solvation stage and provides a more complete set of solvated properties.

SYMMETRY_DECOMPOSITION

Determines symmetry decompositions to calculate.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

0

No symmetry decomposition.

1

Calculate MO eigenvalues and symmetry (if available).

2

Perform symmetry decomposition of kinetic energy and nuclear attraction

matrices.

RECOMMENDATION:

None

SYMMETRY

Controls the efficiency through the use of point group symmetry for calculating integrals.

TYPE:

LOGICAL

DEFAULT:

TRUE

Use symmetry for computing integrals.

OPTIONS:

TRUE

Use symmetry when available.

FALSE

Do not use symmetry. This is always the case for RIMP2 jobs

RECOMMENDATION:

Use default unless benchmarking. Note that symmetry usage is disabled for RIMP2, FFT, and QM/MM jobs.

SYM_IGNORE

Controls whether or not Q-Chem determines the point group of the molecule and reorients the molecule to the standard orientation.

TYPE:

LOGICAL

DEFAULT:

FALSE

Do determine the point group (disabled for RIMP2 jobs).

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

Use default unless you do not want the molecule to be reoriented. Note that symmetry usage is disabled for RIMP2 jobs.

SYM_TOL

Controls the tolerance for determining point group symmetry. Differences in atom locations less than $10^{-\mathrm{SYM\_ TOL}}$ are treated as zero.

TYPE:

INTEGER

DEFAULT:

5

corresponding to $10^{-5}$ .

OPTIONS:

User defined.

RECOMMENDATION:

Use the default unless the molecule has high symmetry which is not being correctly identified. Note that relaxing this tolerance too much may introduce errors into the calculation.

TAO_DFT_THETA_NDP

value of $\theta$ in TAO-DFT.

TYPE:

INTEGER

DEFAULT:

3

OPTIONS:

$n$

$\theta =m\times 10^{-n}$ (hartrees), where $m$ is the value of TAO_DFT_THETA

RECOMMENDATION:

NONE

TAO_DFT_THETA

value of $\theta$ in TAO-DFT.

TYPE:

INTEGER

DEFAULT:

7

OPTIONS:

$m$

$\theta =m\times 10^{-n}$ (hartrees), where $n$ is the value of TAO_DFT_THETA_NDP

RECOMMENDATION:

NONE

TAO_DFT

Controls whether to use TAO-DFT.

TYPE:

Boolean

DEFAULT:

false

OPTIONS:

false

do not use TAO-DFT

true

use TAO-DFT

RECOMMENDATION:

NONE

THRESH_DIIS_SWITCH

The threshold for switching between DIIS extrapolation and direct minimization of the SCF energy is $10^{-\mbox{{\small THRESH\_ DIIS\_ SWITCH}}}$ when SCF_ALGORITHM is DIIS_GDM or DIIS_DM. See also MAX_DIIS_CYCLES

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

User-defined.

RECOMMENDATION:

None

THRESH_RCA_SWITCH

The threshold for switching between RCA and DIIS when SCF_ALGORITHM is RCA_DIIS.

TYPE:

INTEGER

DEFAULT:

3

OPTIONS:

N

Algorithm changes from RCA to DIIS when Error is less than $10^{-N}$ .

RECOMMENDATION:

None

THRESH

Cutoff for neglect of two electron integrals. $10^{-\mathrm{THRESH}}$ (THRESH $\le 14$ ).

TYPE:

INTEGER

DEFAULT:

8

For single point energies.

10

For optimizations and frequency calculations.

14

For coupled-cluster calculations.

OPTIONS:

$n$

for a threshold of $10^{-n}$ .

RECOMMENDATION:

Should be at least three greater than SCF_CONVERGENCE. Increase for more significant figures, at greater computational cost.

TIME_STEP

Specifies the molecular dynamics time step, in atomic units (1 a.u. = 0.0242 fs).

TYPE:

INTEGER

DEFAULT:

None.

OPTIONS:

User-specified.

RECOMMENDATION:

Smaller time steps lead to better energy conservation; too large a time step may cause the job to fail entirely. Make the time step as large as possible, consistent with tolerable energy conservation.

TRANS_ENABLE

Decide whether or not to enable the molecular transport code.

TYPE:

INTEGER

DEFAULT:

0

Do not perform transport calculations.

OPTIONS:

1

Perform transport calculations in the Landauer approximation.

$-1$

Print matrices for subsequent calls for tranchem.exe as a stand-alone post-processing

utility, or for generating bulk model files.

RECOMMENDATION:

Use as required.

TRANX, TRANY, TRANZ

$x$ , $y$ , and $z$ value of user-specified translation (only relevant if ITRNGR is set to 5 or 6

TYPE:

FLOAT

DEFAULT:

0, 0, 0

OPTIONS:

$x$ , $y$ , and $z$ relative to the origin in the appropriate units.

RECOMMENDATION:

None.

TRNSS

Controls whether reduced single excitation space is used

TYPE:

LOGICAL

DEFAULT:

FALSE

Use full excitation space

OPTIONS:

TRUE

Use reduced excitation space

RECOMMENDATION:

None

TRTYPE

Controls how reduced subspace is specified

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

1

Select orbitals localized on a set of atoms

2

Specify a set of orbitals

3

Specify a set of occupied orbitals, include excitations to all virtual orbitals

RECOMMENDATION:

None

UNRESTRICTED

Controls the use of restricted or unrestricted orbitals.

TYPE:

LOGICAL

DEFAULT:

FALSE

(Restricted) Closed-shell systems.

TRUE

(Unrestricted) Open-shell systems.

OPTIONS:

TRUE

(Unrestricted) Open-shell systems.

FALSE

Restricted open-shell HF (ROHF).

RECOMMENDATION:

Use default unless ROHF is desired. Note that for unrestricted calculations on systems with an even number of electrons it is usually necessary to break alpha/beta symmetry in the initial guess, by using SCF_GUESS_MIX or providing $occupied information (see Section 4.4 on initial guesses).

USECUBLAS_THRESH

Sets threshold of matrix size sent to GPU (smaller size not worth sending to GPU).

TYPE:

INTEGER

DEFAULT:

250

OPTIONS:

n

user-defined threshold

RECOMMENDATION:

Use the default value. Anything less can seriously hinder the GPU acceleration

USER_CONNECT

Enables explicitly defined bonds.

TYPE:

STRING

DEFAULT:

FALSE

OPTIONS:

TRUE

Bond connectivity is read from the $molecule section

FALSE

Bond connectivity is determined by atom proximity

RECOMMENDATION:

Set to TRUE if bond connectivity is known, in which case this connectivity must be specified in the $molecule section. This greatly accelerates MM calculations.

USE_MGEMM

Use the mixed-precision matrix scheme (MGEMM) if you want to make calculations in your card in single-precision (or if you have a single-precision-only GPU), but leave some parts of the RI-MP2 calculation in double precision)

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0

MGEMM disabled

1

MGEMM enabled

RECOMMENDATION:

Use when having single-precision cards

VARTHRESH

Controls the temporary integral cut-off threshold. $tmp{\_ }thresh = 10^{-\mathrm{VARTHRESH}}\times DIIS{\_ }error$

TYPE:

INTEGER

DEFAULT:

0

Turns VARTHRESH off

OPTIONS:

$n$

User-defined threshold

RECOMMENDATION:

3 has been found to be a practical level, and can slightly speed up SCF evaluation.

VCI

Specifies the number of quanta involved in the VCI calculation.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

User-defined. Maximum value is 10.

RECOMMENDATION:

The availability depends on the memory of the machine. Memory allocation for VCI calculation is the square of $2*(N_\mathrm {Vib}+N_\mathrm {VCI})/N_\mathrm {Vib}N_\mathrm {VCI}$ with double precision. For example, a machine with 1.5 GB memory and for molecules with fewer than 4 atoms, VCI(10) can be carried out, for molecule containing fewer than 5 atoms, VCI(6) can be carried out, for molecule containing fewer than 6 atoms, VCI(5) can be carried out. For molecules containing fewer than 50 atoms, VCI(2) is available. VCI(1) and VCI(3) usually overestimated the true energy while VCI(4) usually gives an answer close to the converged energy.

VIBMAN_PRINT

Controls level of extra print out for vibrational analysis.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

1

Standard full information print out.

If VCI is TRUE, overtones and combination bands are also printed.

3

Level 1 plus vibrational frequencies in atomic units.

4

Level 3 plus mass-weighted Hessian matrix, projected mass-weighted Hessian

matrix.

6

Level 4 plus vectors for translations and rotations projection matrix.

RECOMMENDATION:

Use default.

WANG_ZIEGLER_KERNEL

Controls whether to use the Wang-Ziegler non-collinear exchange-correlation kernel in a SFDFT calculation.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not use non-collinear kernel

TRUE

Use non-collinear kernel

RECOMMENDATION:

None

WAVEFUNCTION_ANALYSIS

Controls the running of the default wavefunction analysis tasks.

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE

Perform default wavefunction analysis.

FALSE

Do not perform default wavefunction analysis.

RECOMMENDATION:

None

WIG_GRID

Specify angular Lebedev grid for Wigner intracule calculations.

TYPE:

INTEGER

DEFAULT:

194

OPTIONS:

Lebedev grids up to 5810 points.

RECOMMENDATION:

Larger grids if high accuracy required.

WIG_LEB

Use Lebedev quadrature to evaluate Wigner integrals.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Evaluate Wigner integrals through series summation.

TRUE

Use quadrature for Wigner integrals.

RECOMMENDATION:

None

WIG_MEM

Reduce memory required in the evaluation of $W(u,v)$ .

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE

Do not use low memory option.

TRUE

Use low memory option.

RECOMMENDATION:

The low memory option is slower, use default unless memory is limited.

WRITE_WFN

Specifies whether or not a wfn file is created, which is suitable for use with AIMPAC. Note that the output to this file is currently limited to $f$ orbitals, which is the highest angular momentum implemented in AIMPAC.

TYPE:

STRING

DEFAULT:

(NULL)

No output file is created.

OPTIONS:

filename

Specifies the output file name. The suffix .wfn will

be appended to this name.

RECOMMENDATION:

None

XCIS

Do an XCIS calculation in addition to a CIS calculation

TYPE:

LOGICAL

DEFAULT:

False

OPTIONS:

False

Do not do an XCIS calculation

True

Do an XCIS calculation (requires ROHF ground state).

RECOMMENDATION:

None

XC_GRID

Specifies the type of grid to use for DFT calculations.

TYPE:

INTEGER

DEFAULT:

1

SG-1 hybrid

OPTIONS:

0

Use SG-0 for H, C, N, and O, SG-1 for all other atoms.

1

Use SG-1 for all atoms.

2

Low Quality.

$mn$

The first six integers correspond to $m$ radial points and the second six

integers correspond to $n$ angular points where possible numbers of Lebedev

angular points are listed in section 4.3.13.

$-mn$

The first six integers correspond to $m$ radial points and the second six

integers correspond to $n$ angular points where the number of Gauss-Legendre

angular points $n = 2N^2$ .

RECOMMENDATION:

Use default unless numerical integration problems arise. Larger grids may be required for optimization and frequency calculations.

XC_SMART_GRID

Uses SG-0 (where available) for early SCF cycles, and switches to the (larger) grid specified by XC_GRID (which defaults to SG-1, if not otherwise specified) for final cycles of the SCF.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

The use of the smart grid can save some time on initial SCF cycles.

XOPT_SEAM_ONLY

Orders an intersection seam search only, no minimization is to perform.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE

Find a point on the intersection seam and stop.

FALSE

Perform a minimization of the intersection seam.

RECOMMENDATION:

In systems with a large number of degrees of freedom it might be useful to locate the seam first setting this option to TRUE and use that geometry as a starting point for the minimization.

XOPT_STATE_1, XOPT_STATE_2

Specify two electronic states the intersection of which will be searched.

TYPE:

[INTEGER, INTEGER, INTEGER]

DEFAULT:

No default value (the option must be specified to run this calculation)

OPTIONS:

[spin, irrep, state]

spin = 0

Addresses states with low spin,

see also CC_NLOWSPIN.

spin = 1

Addresses states with high spin,

see also CC_NHIGHSPIN.

irrep

Specifies the irreducible representation to which

the state belongs, for $C_{2v}$ point group symmetry

irrep = 1 for $A_1$ , irrep = 2 for $A_2$ ,

irrep = 3 for $B_1$ , irrep = 4 for $B_2$ .

state

Specifies the state number within the irreducible

representation, state = 1 means the lowest excited

state, state = 2 is the second excited state, etc.

0, 0, -1

Ground state.

RECOMMENDATION:

Only intersections of states with different spin or symmetry can be calculated at this time.

XPOL_FIX_MULLIKEN

Control to use self-consistent charge for EE-MBE.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE

Perform an EE-MBE without self-consistent charge.

FALSE

Perform an EE-MBE with self-consistent charge.

RECOMMENDATION:

The charges are derived from isolated monomers without self-consistent process. It is available to use with Mulliken charges, Löwdin charges and CHELPG charges

XPOL_FIX_TIP3P

Use charges corresponding to TIP3P water for EE-MBE.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE

Perform an EE-MBE with charges corresponding to TIP3P water.

FALSE

Do not perform an EE-MBE with charges corresponding to TIP3P water.

RECOMMENDATION:

Only available for water molecules

XPOL_OMEGA

Controls the range-separation parameter, $\omega$ , that is used in long-range-corrected DFT.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE

Use different $\omega$ values for different fragments.

FALSE

Use a single value of $\omega$ for all fragments.

RECOMMENDATION:

If FALSE, the $rem variable OMEGA should be used to specify the single value of $\omega$ . If TRUE, separate values for each fragment should be specified in an $lrc_omega input section. Values in the $lrc_omega section have the same units as the $rem variable OMEGA, namely, $\omega =$ OMEGA/1000, in atomic units.

XPOL

Perform a self-consistent XPol calculation.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE

Perform an XPol calculation.

FALSE

Do not perform an XPol calculation.

RECOMMENDATION:

NONE

Z_EXTRAP_ORDER

Specifies the polynomial order $N$ for Z-vector extrapolation.

TYPE:

INTEGER

DEFAULT:

0

Do not perform $Z$ -vector extrapolation.

OPTIONS:

$N$

Extrapolate using an $N$ th-order polynomial ( $N > 0$ ).

RECOMMENDATION:

None

Z_EXTRAP_POINTS

Specifies the number $M$ of old $Z$ -vectors that are retained for use in extrapolation.

TYPE:

INTEGER

DEFAULT:

0

Do not perform response equation extrapolation.

OPTIONS:

$M$

Save $M$ previous $Z$ -vectors for use in extrapolation $(M>N)$

RECOMMENDATION:

Using the default $Z$ -vector convergence settings, a (4,2)=( $M$ , $N$ ) extrapolation was shown to provide the greatest speedup. At this setting, a 2–3-fold reduction in iterations was demonstrated.

TRUE	Use a dispersion force field.
FALSE	calculate $E_{disp}^{(2)}$ and $E_{exch\text {-}disp}^{(2)}$ .

1	Use the “first generation” (+D1) dispersion potentials from Hesselmann [715, 693].
2	Use the “second generation” (+D2) dispersion potentials from Podeszwa. [716, 694].
3	Use the “third generation” (+D3) dispersion potentials from Lao [695].

TRUE	Compute four-index integrals using the RI approximation.
FALSE	Do not use RI.

S_SQUARED	Compute first order exchange in the single-exchange (“ $S^2$ ") approximation.
S_INVERSE	Compute the exact first order exchange.

MONOMER	Monomer-centered basis set (MCBS).
DIMER	Dimer-centered basis set (DCBS).
PROJECTED	Projected basis set.

TRUE	Evaluate the response corrections and use $E_{ind,resp}^{(2)}$ and $E_{exch\text {-}ind,resp}^{(2)}$
FALSE	Omit these corrections and use $E_{ind}^{(2)}$ and $E_{exch\text {-}ind}^{(2)}$ .

SAPT1	First order SAPT.
SAPT2	Second order SAPT.
ELST	First-order Rayleigh-Schrödinger perturbation theory.
RSPT	Second-order Rayleigh-Schrödinger perturbation theory.

MBCP	Use many-body counterpoise correction.
VMFC	Use Valiron-Mayer function counterpoise correction.

GAS	No electrostatic embedding; monomers are in the gas phase.
CHARGES	Charge embedding.
DENSITY	Density embedding.

OFF	disables fEFP
LA	enables fEFP with the Link Atom (HLA or CLA) scheme (only electrostatics and polarization)
MFCC	enables fEFP with MFCC (only electrostatics)

OFF	disables fEFP_QM and performs a QM/EFP calculation
LA	enables fEFP_QM with the Link Atom scheme

QLOWDIN	Löwdin charges.
QMULLIKEN	Mulliken charges.
QCHELPG	CHELPG charges.

1170	Optimized value $c_ c=1.17$ for ADC(2)-s or
1000	$c_ c=1.0$ for ADC(2)-x

TRUE	Use DIIS algorithm.
FALSE	Do diagonalization using Davidson algorithm.

0	Quiet: almost only results are printed.
1	Normal: basic status information and results are printed.
2	Debug1: more status information, extended information on timings.
...

TRUE	Calculate state-to-state transition properties.
FALSE	Do not compute transition properties between excited states.

TRUE	Calculate excited state properties.
FALSE	Do not compute state properties.

TRUE	Calculate two-photon absorption cross-sections.
FALSE	Do not compute two-photon absorption cross-sections.

THERMAL	Random sampling of nuclear velocities from a Maxwell-Boltzmann
	distribution. The user must specify the temperature in Kelvin via
	the $rem variable AIMD_TEMP.
ZPE	Choose velocities in order to put zero-point vibrational energy into
	each normal mode, with random signs. This option requires that a
	frequency job to be run beforehand.
QUASICLASSICAL	Puts vibrational energy into each normal mode. In contrast to the
	ZPE option, here the vibrational energies are sampled from a
	Boltzmann distribution at the desired simulation temperature. This
	also triggers several other options, as described below.

BOMD	Born-Oppenheimer molecular dynamics.
CURVY	Curvy-steps Extended Lagrangian molecular dynamics.

0	Do not compute dipole autocorrelation function.
$1\leq n \leq \mbox{{\small AIMD\_ STEPS}}$	Compute dipole autocorrelation function for last $n$
	timesteps of the trajectory.

$1\leq n \leq \mbox{{\small AIMD\_ STEPS}}$	Update the velocity/dipole autocorrelation function
	every $n$ steps.

0	Do not compute velocity autocorrelation function.
$1\leq n \leq \mbox{{\small AIMD\_ STEPS}}$	Compute velocity autocorrelation function for last $n$
	time steps of the trajectory.

TRUE	Carry out the anharmonic frequency calculation.
FALSE	Do harmonic frequency calculation.

Symbol. Use standard basis sets as per Chapter 7.
BASIS2_GEN	General BASIS2
BASIS2_MIXED	Mixed BASIS2

FOPPROJECTION	Construct the Fock matrix in the second basis
OVPROJECTION	Projects MO’s from BASIS2 to BASIS.

General, Gen	User defined ($basis keyword required).
Symbol	Use standard basis sets as per Chapter 7.
Mixed	Use a mixture of basis sets (see Chapter 7).

0	Do not perform localize the occupied space.
1	Allow core-valence mixing in Boys localization.
2	Localize core and valence separately.

1	Standard GVBMAN guess (orbital localization via GVB_LOCAL + Sano procedure).
2	Use orbitals from previous GVBMAN calculation, along with SCF_GUESS = read.
3	Convert UHF orbitals into pairing VB form.

1	Standard CCVB model
3	Independent electron pair approximation (IEPA) to CCVB
4	Variational PP (the CCVB reference energy)