- Search

(February 4, 2022)

BASIS

BASIS

Specifies the electronic 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 8.
Mixed
Use a mixture of basis sets (see Chapter 8).

RECOMMENDATION:

Consult literature and reviews to aid your selection.

CONCENTRIC_REF_BASIS

CONCENTRIC_REF_BASIS

Specify the projection basis (PB) in the concentric localization procedure

TYPE:

STRING

DEFAULT:

NONE

OPTIONS:

Parsed in the same way as BASIS; if unspecified, the working basis (WB) will be used as PB.

RECOMMENDATION:

WB is usually a good choice; a smaller basis can chosen with caution to further
reduce the computational cost.

CONCENTRIC_VIRTS_ZETA

CONCENTRIC_VIRTS_ZETA

Specify the size of the truncated virtual space

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

$m$
The total number of the CL-truncated virtuals is $m\times {n}_{\text{occ}}^{\text{active}}$

RECOMMENDATION:

Use the default; set it to a larger value if higher accuracy is requested.

CONCENTRIC_VIRTS

CONCENTRIC_VIRTS

Use the concentric localization (CL) scheme to truncate the virtual space

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE
Use the CL scheme to truncate the virtual space
FALSE
Leave the virtual space untruncated

RECOMMENDATION:

Use CL truncation for WFT-in-DFT calculations.

CVS_IP_ALPHA

CVS_IP_ALPHA

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

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0
Do not look for any IP/$\alpha $ states.

OPTIONS:

$[i,j,k\mathrm{\dots}]$
Find $i$ ionized states in the first irrep, $j$ states
in the second irrep *etc.*

RECOMMENDATION:

None

CVS_IP_BETA

CVS_IP_BETA

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

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0
Do not look for any IP/$\beta $ states.

OPTIONS:

$[i,j,k\mathrm{\dots}]$
Find $i$ ionized states in the first irrep, $j$ states
in the second irrep *etc.*

RECOMMENDATION:

None

CVS_IP_STATES

CVS_IP_STATES

Sets the number of core-ionized states to find. By default, $\beta $ electron will be removed.

TYPE:

INTEGER/INTEGER ARRAY

DEFAULT:

0
Do not look for any IP states.

OPTIONS:

[i,j,k…]
Find $i$ ionized states in the first irrep, $j$ states in the second irrep *etc.*

RECOMMENDATION:

None

DIRECT_DIAG

DIRECT_DIAG

Perform direct diagonalization to obtain all the NEO excitation energies.

TYPE:

INTEGER

DEFAULT:

0
Use Davidson algorithm.

OPTIONS:

1
Do the direct diagonalization.
0
Use Davidson algorithm.

RECOMMENDATION:

Only use this option when Davidson solutions are not stable.

DISTORT

DISTORT

Specifies whether to apply pressure or external force to a chemical system

TYPE:

LOGICAL

DEFAULT:

False

OPTIONS:

False
Do not use pressure or force
True
Use pressure or force

RECOMMENDATION:

Set to true to apply pressure or force.

EDA2_MOM

EDA2_MOM

Perform ALMO-EDA calculation with non-aufbau electronic configurations
using MOM

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

FALSE
Standard ALMO-EDA calculation
TRUE
ALMO-EDA for non-aufbau states

RECOMMENDATION:

None

EDA_ALIGN_FRGM_SPIN

EDA_ALIGN_FRGM_SPIN

Turn on the fragment spin alignment procedure

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Do not performed the spin alignment procedure (turned on by default in unrestricted cases)
1
Perform fragment spin alignment; use GDM for the polarization step preceding the MOM calculations
2
Perform fragment spin alignment; use GDM and perform stability analysis for the polarization step

RECOMMENDATION:

Use 1 or 2 when the radical is of highly symmetric structure

EDA_NOCV

EDA_NOCV

Perform the NOCV analysis and plot the significant NOCVs

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Do not perform NOCV analysis
1
Plot NOCV pair contributions to density deformation
2
Plot both NOCV pair contribution to density deformation and NOCV orbitals

RECOMMENDATION:

None

EDA_PLOT_DIFF_DEN

EDA_PLOT_DIFF_DEN

Plot changes in electron density due to POL and CT

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

FALSE
Do not make EDD plots
TRUE
Make EDD plots

RECOMMENDATION:

None

EIGSLV_METH

EIGSLV_METH

Control the method for solving the ALMO-CIS eigen-equation

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Explicitly build the Hamiltonian then diagonalize (full-spectrum).
1
Use the Davidson method (currently only available for restricted cases).

RECOMMENDATION:

None

ENV_METHOD

ENV_METHOD

Specify the low-level theory in a projection-based embedding calculation

TYPE:

STRING

DEFAULT:

NONE

OPTIONS:

Parsed in the same way as *$rem* variable “METHOD”

RECOMMENDATION:

A mean-field method (pure or hybrid density functional) should be chosen.

ESP_EFIELD

ESP_EFIELD

Triggers the calculation of ESP and/or E-field at nuclear positions or on a given
grid of points

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Compute ESP only
1
Compute both ESP and electric field
2
Compute electric field only

RECOMMENDATION:

None

EX_EDA

EX_EDA

Perform an ALMO-EDA calculation with one or more fragments excited.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE
Perform EDA with excited-state molecule(s) taken into account.
FALSE

RECOMMENDATION:

None

FIXING_V_EMBED

FIXING_V_EMBED

Invoke the linearized approximation for the energy functional used for embedding calculations

TYPE:

BOOLEAN

DEFAULT:

TRUE

OPTIONS:

TRUE
Use the linearized approximation for energy functional [Eq. (11.99)]
FALSE
Use the original energy functional [Eq. (11.93)]

RECOMMENDATION:

Use the default to achieve savings in computational costs

FODFT_DONOR

FODFT_DONOR

Specify the donor fragment in FODFT calculation

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

1
First fragment as donor
2
Second fragment as donor

RECOMMENDATION:

With FODFT_METHOD = 1, the charged fragment needs to be the
donor fragment

FODFT_METHOD

FODFT_METHOD

Specify the flavor of FODFT method

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

1
FODFT($2\mathrm{n}-1$)@${D}^{+}A$ (HT) / FODFT($2\mathrm{n}+1$)@${D}^{-}A$ (ET)
2
FODFT($2\mathrm{n}$)@$DA$
3
FODFT($2\mathrm{n}-1$)@$DA$ (HT) / FODFT($2\mathrm{n}+1$)@${D}^{-}{A}^{-}$ (ET)

RECOMMENDATION:

The default approach shows the best overall performance

FRAG_DIABAT_DOHT

FRAG_DIABAT_DOHT

Specify whether hole or electron transfer is considered

TYPE:

BOOLEAN

DEFAULT:

TRUE

OPTIONS:

TRUE
Do hole transfer
FALSE
Do electron transfer

RECOMMENDATION:

Need to be specified for POD and FODFT calculations

FRAG_DIABAT_METHOD

FRAG_DIABAT_METHOD

Specify fragment based diabatization method

TYPE:

STRING

DEFAULT:

NONE

OPTIONS:

ALMO_MSDFT
Perform ALMO(MSDFT) diabatization
POD
Perform projection operator diabatization (the original method)
POD2_L
Perform POD2 with Löwdin orthogonalization
POD2_GS
Perform POD2 with Grad-Schmidt orthogonalization
ESID
The energy-split-in-dimer method,^{1143} which is equivalent to
the FMO approach
introduced in Section 10.14.2.5
FODFT
Calculate electronic coupling using fragment orbital DFT

RECOMMENDATION:

NONE

FRAG_DIABAT_PRINT

FRAG_DIABAT_PRINT

Specify the print level for fragment based diabatization calculations

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
No additional prints
$\ge 1$
Print additional details

RECOMMENDATION:

Use the default unless debug information is needed

GAP_TOL

GAP_TOL

HOMO/LUMO gap threshold to control whether to shift the diagonal elements of the virtual block of the Fock matrix or not.
If the HOMO/LUMO gap is less than this threshold, at a given SCF iteration, then
the diagonal elements of the virtual block of the Fock matrix are shifted. Otherwise no level-shift is applied.

TYPE:

INTEGER

DEFAULT:

300

OPTIONS:

User-defined

RECOMMENDATION:

The input number must be an integer between 0 and 9999.
The actual threshold is equal to GAP_TOL divided by 1000, in Hartree.
The default value is provided to make the level-shifting calculation run and should not be taken as optimal for any specific problem.
Trial and error may be required to find the optimal threshold.
Larger values of GAP_TOL generally lead to
level-shifting being used more frequently during the SCF convergence process.

GEN_SCFMAN_EMBED

GEN_SCFMAN_EMBED

Run a projection-based embedding calculation using the implementation
based onGEN_SCFMAN

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE
Perform a projection-based embedding calculation
FALSE
Do not perform an embedding calculation

RECOMMENDATION:

None

GUESS_GRID

GUESS_GRID

Specifies the type of grid to use for SAP guess generation. The options are the same as those of the *$rem* variable XC_GRID.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

0
Use SG-0 for H, C, N, and O; SG-1 for all other atoms.
$n$
Use SG-$n$ for all atoms, $n=1,2$, or 3
$XY$
A string of two six-digit integers $X$ and $Y$, where $X$ is the number of radial points
and $Y$ is the number of angular points where possible numbers of Lebedev angular
points, which must be an allowed value from Table 5.2 in
Section 5.5.
$-XY$
Similar format for Gauss-Legendre grids, with the six-digit integer $X$ corresponding
to the number of radial points and the six-digit integer $Y$ providing the number of
Gauss-Legendre angular points, $Y=2{N}^{2}$.

RECOMMENDATION:

Larger grids may be required if the SAP guess is poor.

JOBTYPE

JOBTYPE

Specifies the calculation.

TYPE:

STRING

DEFAULT:

Default is single-point, which should be changed to one of the following options.

OPTIONS:

OPT
Equilibrium structure optimization.
TS
Transition structure optimization is currently not available in NEO.
RPATH
Intrinsic reaction path following is currently not available in NEO.

RECOMMENDATION:

Application-dependent. Always use SYM_IGNORE = 1 with geometry optimization.

LEVEL_SHIFT

LEVEL_SHIFT

Determine whether to invoke level-shifting or not together with DIIS.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TURE, FALSE

RECOMMENDATION:

Use TRUE if level-shifting is necessary to accelerate SCF convergence.

LSHIFT

LSHIFT

Constant shift applied to all diagonal elements of the virtual block of the Fock matrix.

TYPE:

INTEGER

DEFAULT:

200

OPTIONS:

User-defined

RECOMMENDATION:

The input number must be an integer between 0 and 9999.
The actual shift is equal to GAP_TOL divided by 1000, in Hartree.
The default value is provided to make the level-shifting calculation run and should not be taken as optimal for any specific problem.
Trial and error may be required to find the optimal threshold.
Larger level shifts make the SCF process more stable but also slow down convergence, thus requiring more SCF cycles.

MAX_DP_CYCLES

MAX_DP_CYCLES

The maximum number of SCF iterations with damping when SCF_ALGORITHM = DP_DIIS and DP_GDM. See also THRESH_DP_SWITCH.

TYPE:

INTEGER

DEFAULT:

3

OPTIONS:

1
Only a single SCF step with damping, and no damping for the remaining SCF steps.
$n$
$n$ SCF iterations with damping before turning damping off.

RECOMMENDATION:

Increase this number if strong fluctuation continues after damping is turned off.

MAX_LS_CYCLES

MAX_LS_CYCLES

The maximum number of DIIS iterations with level-shifting when SCF_ALGORITHM = LS_DIIS. See also THRESH_LS_SWITCH.

TYPE:

INTEGER

DEFAULT:

MAX_SCF_CYCLES

OPTIONS:

1
Only a single DIIS step with level-shifting, and no level-shifting for the remaining DIIS steps.
$n$
$n$ DIIS iterations with level-shifting before turning level-shifting off.

RECOMMENDATION:

None

MAX_SCF_CYCLES

MAX_SCF_CYCLES

Controls the maximum number of SCF iterations permitted.

TYPE:

INTEGER

DEFAULT:

50

OPTIONS:

$n$
$n>0$ User-selected.

RECOMMENDATION:

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

METHOD

METHOD

Specifies the exchange-correlation functional.

TYPE:

STRING

DEFAULT:

No default

OPTIONS:

*NAME*
Use METHOD = *NAME*, where *NAME* is one of the following:
HF for Hartree-Fock theory;
one of the DFT methods listed in Section 5.3.5.;

RECOMMENDATION:

In general, consult the literature to guide your selection. Our recommendations for DFT are indicated
in bold in Section 5.3.5.

MOM_METHOD

MOM_METHOD

Determines the target orbitals with which to maximize the overlap on each SCF cycle.

TYPE:

INTEGER

DEFAULT:

MOM

OPTIONS:

MOM
Maximize overlap with the orbitals from the previous SCF cycle.
IMOM
Maximize overlap with the initial guess orbitals.

RECOMMENDATION:

If appropriate guess orbitals can be obtained, then IMOM
can provide more reliable convergence to the desired solution.^{60}

MSDFT_METHOD

MSDFT_METHOD

Specify the scheme for ALMO(MSDFT)

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

1
The original MSDFT scheme [Eq. (10.134)]
2
The ALMO(MSDFT2) approach [Eq. (10.137)]

RECOMMENDATION:

Use the default method. Note that the method will be automatically
reset to 1 if a meta-GGA functional is requested.

MSDFT_PINV_THRESH

MSDFT_PINV_THRESH

Set the threshold for pseudo-inverse of the interstate overlap

TYPE:

INTEGER

DEFAULT:

4

OPTIONS:

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

RECOMMENDATION:

Use the default value

NDAMP

NDAMP

Determine the mixing coefficient. $\alpha $ = NDAMP/100.

TYPE:

INTEGER

DEFAULT:

75

OPTIONS:

User-defined. Integers between 0 and 100.

RECOMMENDATION:

Increase NDAMP if strong fluctuations happen during the SCF process.

NEO_BASIS_LIN_DEP_THRESH

NEO_BASIS_LIN_DEP_THRESH

This keyword is used to set the liner dependency threshold for nuclear basis sets. It is defined as ${10}^{-\mathrm{NEO}\mathrm{\_}\mathrm{BASIS}\mathrm{\_}\mathrm{LIN}\mathrm{\_}\mathrm{DEP}\mathrm{\_}\mathrm{THRESH}}$.

TYPE:

DOUBLE

DEFAULT:

5.0

OPTIONS:

User-defined

RECOMMENDATION:

No recommendation.

NEO_EPC

NEO_EPC

Specifies the electron-proton correlation functional.

TYPE:

STRING

DEFAULT:

No default

OPTIONS:

*NAME*
Use NEO_EPC = *NAME*, where *NAME* can be either epc172 or epc19.

RECOMMENDATION:

Consult the NEO literature to guide your selection.

NEO_E_CONV

NEO_E_CONV

Energy convergence criteria in the NEO-SCF calculations so that the difference in energy between electronic and protonic iterations is less than ${10}^{-\mathrm{NEO}\mathrm{\_}\mathrm{E}\mathrm{\_}\mathrm{CONV}}$.

TYPE:

INTEGER

DEFAULT:

8

OPTIONS:

User-defined

RECOMMENDATION:

Tighter criteria for geometry optimization are recommended.

NEO_ISOTOPE

NEO_ISOTOPE

Enable calculations of different types of isotopes. Only one type of isotope is allowed at present.

TYPE:

INTEGER

DEFAULT:

1
Default is the proton isotope.

OPTIONS:

1
This NEO calculation is using proton isotope.
2
This NEO calculation is using deuterium isotope.
3
This NEO calculation is using tritium isotope.

RECOMMENDATION:

Refer to the NEO literature for the best performance on the isotope effects calculations.

NEO_N_SCF_CONVERGENCE

NEO_N_SCF_CONVERGENCE

NEO-SCF is considered converged when the nuclear wave function error is less that
${10}^{-\mathrm{NEO}\mathrm{\_}\mathrm{N}\mathrm{\_}\mathrm{SCF}\mathrm{\_}\mathrm{CONVERGENCE}}$.

TYPE:

INTEGER

DEFAULT:

7

OPTIONS:

User-defined

RECOMMENDATION:

None.

NEO_PURECART

NEO_PURECART

This keyword is used to specify Cartesian or spherical Gaussians for nuclear basis functions.

TYPE:

INTEGER

DEFAULT:

2222

OPTIONS:

User-defined

RECOMMENDATION:

Default are Cartesian Gaussians. 1111 would define spherical Gaussians similar to keyword PURECART. Current NEO calculations do not support Cartesian electronic or nuclear basis sets with h angular momentum.

NEO_VPP

NEO_VPP

Remove $J-K$ terms from the nuclear Fock matrix and the corresponding kernel terms for NEO excited state methods for the case of one quantum proton.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

1
Enable this option.
0
Disable this option.

RECOMMENDATION:

Use this only in the case of one quantum hydrogen.

NEO

NEO

Enable a NEO-SCF calculation.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE
Enable a NEO-SCF calculation.
FALSE
Disable a NEO-SCF calculation.

RECOMMENDATION:

Set to TRUE if desired.

POD_MULTI_PAIRS

POD_MULTI_PAIRS

Calculate the couplings between multiple pairs of donor and acceptor
orbitals in POD

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE
Calculate the couplings between multiple pairs of orbitals
FALSE
Only calculate the D(HOMO)–A(HOMO) coupling (for HT) or
D(LUMO)–A(LUMO) coupling (for ET)

RECOMMENDATION:

None

POD_WINDOW

POD_WINDOW

Specify the number of donor and acceptor orbitals when couplings between
multiple pairs are requested

TYPE:

INTEGER

DEFAULT:

5

OPTIONS:

$n$
Including $n$ frontier occupied orbitals (from $\mathrm{HOMO}-n+1$ to HOMO)
and $n$ frontier virtual orbitals (from LUMO to $\mathrm{LUMO}+n-1$) for both
donor and acceptor

RECOMMENDATION:

None

RR_NO_NORMALISE

RR_NO_NORMALISE

Controls whether frequency job calculates resonance-Raman intensities

TYPE:

LOGICAL

DEFAULT:

False

OPTIONS:

False
Normalise RR intensities
True
Doesn’t normalise RR intensities

RECOMMENDATION:

False

SCFMI_MOM

SCFMI_MOM

Perform an SCFMI calculation with non-aufbau electronic configurations
using MOM

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

FALSE
Standard SCFMI calculation
TRUE
SCFMI calculation with MOM

RECOMMENDATION:

None

SCF_ALGORITHM

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:

In the NEO methods, the GDM procedure is recommended.

SCF_CONVERGENCE

SCF_CONVERGENCE

NEO-SCF is considered converged when the electronic wave function error is less that
${10}^{-\mathrm{SCF}\mathrm{\_}\mathrm{CONVERGENCE}}$. Adjust the value of THRESH at the same
time. (Starting with Q-Chem 3.0, the DIIS error is measured by the maximum error
rather than the RMS error as in earlier versions.)

TYPE:

INTEGER

DEFAULT:

5
For single point energy calculations.
8
For geometry optimizations.

OPTIONS:

User-defined

RECOMMENDATION:

None.

SET_CISGUES

SET_CISGUES

Controls how to generate the initial guess excitation vectors in CIS/TDA/RPA calculations.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Generate N (no. of roots requested) occupied$\to $virtual single orbital transitions according to their orbital energy difference order (from low to high). This is the common scenario.
1
Generate N-1 occupied$\to $virtual single orbital transitions according to their orbital energy difference order (from low to high), and generate another guess excitation vector consist of all the remaining single orbital transitions in the occupied$\to $virtual transition space with equal weights.
2
Generate N occupied/virtual single orbital transitions according to their orbital energy difference order (from low to high), and generate one more guess excitation vector consist of all the remaining single orbital transitions in the occupied$\to $virtual transition space with equal weights.

RECOMMENDATION:

The default setting should work for most of the cases. However, when the no. of roots is small, in some CIS/TDA/RPA calculations low energy excited states could be missing. The options SET_CISGUES = 1 or 2 may remedy this root missing issue by sampling more vectors in the transition space. Setting SET_CISGUES = 1 or 2 may take more cycles to converge in the Davidson iteration, but the results are expected to be more reliable. Currently SET_CISGUES = 1 or 2 are not supported in SF-XCIS calculations. Setting TRNSS = TRUE also disables the setting of SET_CISGUES.

SET_ROOTS

SET_ROOTS

Sets the number of NEO excited state roots to find by Davidson or display the number of roots obtained by direct diagonalization.

TYPE:

INTEGER

DEFAULT:

0
Do not look for any excited states.

OPTIONS:

$n$
$n>0$ Looks for $n$ NEO excited states.

RECOMMENDATION:

None

SET_RPA

SET_RPA

Do a NEO-TDDFT or NEO-TDHF calculation.

TYPE:

LOGICAL/INTEGER

DEFAULT:

FALSE

OPTIONS:

FALSE
Do a NEO-TDA or NEO-CIS calculation.
TRUE
Do a NEO-TDDFT or NEO-TDHF calculation.

RECOMMENDATION:

Consult the NEO literature to guide your selection.

SPADE_PARTITION

SPADE_PARTITION

Use the SPADE approach to determine the initial set of embedded (active) orbitals

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE
Use SPADE to partition the occupied space
FALSE
Use the Pipek-Mezey localization + Mulliken population to assign occupied orbitals

RECOMMENDATION:

Use SPADE if a significant gap in the spectrum of singular values can be detected.

THRESH_DP_SWITCH

THRESH_DP_SWITCH

The threshold for turning off damping in SCF iterations is ${10}^{-\text{THRESH\_DP\_SWITCH}}$ when
SCF_ALGORITHM is set to DP_DIIS or DP_GDM. See also MAX_DP_CYCLES.

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

User-defined.

RECOMMENDATION:

None

THRESH_LS_SWITCH

THRESH_LS_SWITCH

The threshold for turning off level-shifting in DIIS is ${10}^{-\text{THRESH\_LS\_SWITCH}}$ when
SCF_ALGORITHM is set to LS_DIIS. See also MAX_LS_CYCLES.

TYPE:

INTEGER

DEFAULT:

4

OPTIONS:

User-defined.

RECOMMENDATION:

None

UNRESTRICTED

UNRESTRICTED

Controls the use of restricted or unrestricted orbitals.

TYPE:

LOGICAL

DEFAULT:

FALSE
Closed-shell systems.
TRUE
Open-shell systems.

OPTIONS:

FALSE
Constrain the spatial part of the alpha and beta orbitals to be the same.
TRUE
Do not Constrain the spatial part of the alpha and beta orbitals.

RECOMMENDATION:

The ROHF method is not available. 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).

VFB_CTA

VFB_CTA

Use the Variational Forward-Backward (VFB) approach to obtain “one-way” CT PESs.

TYPE:

STRING

DEFAULT:

NONE

OPTIONS:

FORWARD
Allow 1$\to $2 CT only (1 and 2 are two fragments).
BACKWARD
Allow 2$\to $1 CT only.

RECOMMENDATION:

None

XC_GRID

XC_GRID

Specifies the type of grid to use for DFT calculations.

TYPE:

INTEGER

DEFAULT:

Functional-dependent; see Table 5.3.

OPTIONS:

0
Use SG-0 for H, C, N, and O; SG-1 for all other atoms.
$n$
Use SG-$n$ for all atoms, $n=1,2$, or 3
$XY$
A string of two six-digit integers $X$ and $Y$, where $X$ is the number of radial points
and $Y$ is the number of angular points where possible numbers of Lebedev angular
points, which must be an allowed value from Table 5.2 in
Section 5.5.
$-XY$
Similar format for Gauss-Legendre grids, with the six-digit integer $X$ corresponding
to the number of radial points and the six-digit integer $Y$ providing the number of
Gauss-Legendre angular points, $Y=2{N}^{2}$.

RECOMMENDATION:

Use the default unless numerical integration problems arise. Larger grids may be
required for optimization and frequency calculations.

FRZN_OPT

FRZN_OPT

Controls whether the job uses zeroed Hessian technique in the frequency calculations

TYPE:

LOGICAL

DEFAULT:

False

OPTIONS:

False
Do not use the zeroed out Hessian
True
Use the zeroed out Hessian

RECOMMENDATION:

False

FRZ_ATOMS

FRZ_ATOMS

Controls the number of frozen atoms

TYPE:

INTEGER

DEFAULT:

No default

OPTIONS:

User defined

RECOMMENDATION:

None

HARM_FORCE

HARM_FORCE

Sets the force constant for harmonic confiner

TYPE:

INTEGER

DEFAULT:

No default

OPTIONS:

User defined

RECOMMENDATION:

None

HARM_OPT

HARM_OPT

Controls whether the job uses confining potentials

TYPE:

LOGICAL

DEFAULT:

False

OPTIONS:

False
Do not use the potential
True
Use the potential

RECOMMENDATION:

False

HOATOMS

HOATOMS

Controls the number of confined atom

TYPE:

INTEGER

DEFAULT:

No default

OPTIONS:

User defined

RECOMMENDATION:

None

CLENSHAW_NGRID

CLENSHAW_NGRID

Number of grid points for the Curtis-Clenshaw quadrature.

TYPE:

INTEGER

DEFAULT:

40

OPTIONS:

RECOMMENDATION:

Use default.

COMPLEX_EXPONENTS

COMPLEX_EXPONENTS

Enable a non-Hermitian calculation with CBFs.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Perform a non-Hermitian calculation with CBFs

RECOMMENDATION:

Set to TRUE if a non-Hermitian calculation using CBFs is desired.

COMPLEX_METSCF

COMPLEX_METSCF

Specify the NH-SCF solver

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

0
Roothaan iterations
1
DIIS
3
ADIIS
21
Newton-MINRES

RECOMMENDATION:

Use the default (DIIS).

COMPLEX_N_ELECTRON

COMPLEX_N_ELECTRON

Add electrons for non-Hermitian calculation.

TYPE:

INTEGER

DEFAULT:

0
Perform the non-Hermitian calculation on $N$-electrons

OPTIONS:

$n$
Perform the non-Hermitian calculation on an $N+n$ electron system

RECOMMENDATION:

None

COMPLEX_SCF_GUESS

COMPLEX_SCF_GUESS

Specify the NH-SCF guess

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Use a guess from a static-exchange calculation
1
Read real-basis MO coefficients
2
Read real-basis density matrix
1000
Read guess from a previous calculation

RECOMMENDATION:

Use a guess from a static exchange calculation. Note that for temporary anions, this requires the specification of COMPLEX_TARGET.

COMPLEX_SCF

COMPLEX_SCF

Perform a non-Hermitian SCF calculation with CBFs

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Do not perform an NH-SCF calculation
1
Perform a restricted NH-SCF calculation
2
Perform an unrestricted NH-SCF calculation
3
Perform a restricted, open-shell NH-SCF calculation

RECOMMENDATION:

None

COMPLEX_SPIN_STATE

COMPLEX_SPIN_STATE

Spin state for non-Hermitian calculation

TYPE:

INTEGER

DEFAULT:

1
Singlet

OPTIONS:

$2S+1$
A state of spin $S$

RECOMMENDATION:

None

COMPLEX_STATIC_EXCHANGE

COMPLEX_STATIC_EXCHANGE

Perform a CBF static-exchange calculation.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Perform a static exchange calculation
FALSE
Do not perform a static exchange calculation

RECOMMENDATION:

Set to TRUE if a static-exchange calculation is desired.

COMPLEX_TARGET

COMPLEX_TARGET

Specify the orbital index to be occupied for a temporary anion

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$
Orbital index (starting at zero) for the additional electron

RECOMMENDATION:

$n$ should always be greater than ${N}_{\text{occ}}-1$.

NOCIS

NOCIS

Run a NOCIS calculation

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

False
Do not run a NOCIS calculation.
True
Run a NOCIS calculation.

RECOMMENDATION:

This variable must be set to true to run a NOCIS or a 1C-NOCIS calculation.

NOCI_DETGEN

NOCI_DETGEN

Control how the multiple determinants for NOCI are created.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Use only the initial reference determinants.
1
Generate CIS excitations from each reference determinant.
2
Generate all FCI excitations from each reference determinant.
3
Generate $n$ multiple determinants using SCF metadynamics, where $n$ is specified
using SCF_SAVEMINIMA = $n$.
4
Generate all CAS excitations from each reference determinant, where the active orbitals
are specified using the *$active_orbitals* input section.

RECOMMENDATION:

By default, these multiple determinants are optimized at the SCF level before
running NOCI. This behavior can be turned off using by specifying
SKIP_SCFMAN = TRUE.

NOCI_NEIGVAL

NOCI_NEIGVAL

The number of NOCI eigenvalues to be printed.

TYPE:

INTEGER

DEFAULT:

10

OPTIONS:

$n$
Positive integer

RECOMMENDATION:

Increase this to print progressively higher NOCI energies.

NOCI_REFGEN

NOCI_REFGEN

Control how the initial reference determinants are created.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Generate initial reference determinant from a single SCF calculation.
1
Read (multiple) initial reference determinants from a previous calculation.

RECOMMENDATION:

The specific reference determinants to be read from a previous calculation
can be indicated using SCF_READMINIMA.

NUM_REF

NUM_REF

Set the number of atoms (references) to be included in the excitation calculation

TYPE:

Integer

DEFAULT:

None

OPTIONS:

$n$
Positive integer

RECOMMENDATION:

This variable determines the number of references for the calculation. As an example, for the oxygen K-edge in CO${}_{2}$, the number of references would be would be 2 (two oxygen atoms), whereas for carbon it would be 1 (one carbon atom).

ONE_CENTER

ONE_CENTER

Run a 1C-NOCIS calculation

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

False
Run a NOCIS calculation.
True
Run a 1C-NOCIS calculation.

RECOMMENDATION:

This variable must be set to true to run a 1C-NOCIS calculation, and NOCIS must be set to true as well.

ORB_OFFSET

ORB_OFFSET

Determine the starting orbital for a NOCIS/STEX/1C-NOCIS calculation

TYPE:

Integer

DEFAULT:

None

OPTIONS:

$n$
Non-negative integer

RECOMMENDATION:

This variable determines the starting orbital for the calculation. As an example, for the oxygen K-edge in CO${}_{2}$, the starting orbital would be 0, whereas for carbon it would be 2.

REL_X2C_FD_DISPLACEMENT

REL_X2C_FD_DISPLACEMENT

Controls finite difference step for calulating W

TYPE:

INTEGER

DEFAULT:

100

OPTIONS:

$n$
Set finite difference step to $n\times {10}^{-6}$

RECOMMENDATION:

None

REL_X2C

REL_X2C

Enables X2C scalar relativistic calculation

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Perform a regular, non-relativistic SCF calculation
1
Perform a scalar relativistic X2C calculation

RECOMMENDATION:

Set to 1 if a scalar relativistic X2C calculation is desired.

SCF_EESCALE_ARG

SCF_EESCALE_ARG

Control the phase angle of the complex $\lambda $ electron-electron scaling.

TYPE:

INTEGER

DEFAULT:

$00000$ meaning $0.0000$

OPTIONS:

$abcde$ corresponding to $a.bcde$

RECOMMENDATION:

A complex phase angle of $00500$, meaning $0.0500$, is usually
sufficient to follow a solution safely past the Coulson-Fischer point
and onto its complex holomorphic counterpart.

SCF_EESCALE_MAG

SCF_EESCALE_MAG

Control the magnitude of the $\lambda $ electron-electron scaling.

TYPE:

INTEGER

DEFAULT:

$10000$ meaning $1.0000$

OPTIONS:

$abcde$ corresponding to $a.bcde$

RECOMMENDATION:

For holomorphic Hartree-Fock orbitals, only the magnitude of the input is used, while
for real Hartree-Fock orbitals, the input sign indicates the sign of $\lambda $.

SCF_HOLOMORPHIC

SCF_HOLOMORPHIC

Turn on the use of holomorphic Hartree-Fock orbitals.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE
Holomorphic Hartree-Fock is turned off
TRUE
Holomorphic Hartree-Fock is turned on.

RECOMMENDATION:

If TRUE, holomorphic Hartree-Fock complex orbital coefficients will always be used.
If FALSE, but COMPLEX = TRUE, complex Hermitian orbitals will be used.

STEX

STEX

Run a STEX calculation

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

False
Do not run a STEX calculation.
True
Run a STEX calculation.

RECOMMENDATION:

This variable must be set to true to run a STEX calculation. NOCIS cannot be set to true.

USE_LIBNLQ

USE_LIBNLQ

Turn on the use of LIBNLQ for calculating nonlocal correlation funcitonal.

TYPE:

LOGICAL

DEFAULT:

True
For VV10.
FALSE
For all other nonlocal funcitonals.

OPTIONS:

False
True

RECOMMENDATION:

Use the default

USE_LIBNOCI

USE_LIBNOCI

Turn on the use of libnoci for running NOCI calculations.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

False
Do not use libnoci (uses original Q-Chem implementation).
True
Use the libnoci implementation.

RECOMMENDATION:

The *$rem* variables detailed below are only available in libnoci.

EDA_COVP_THRESH

EDA_COVP_THRESH

Specifies the significance above which the COVPs will be saved

TYPE:

INTEGER

DEFAULT:

5

OPTIONS:

$N$
COVPs that accounts for more than $N$% of the fragment-wise energy or charge transfer will be saved

RECOMMENDATION:

None

EDA_PCT_A

EDA_PCT_A

Perform perturbative CT analysis

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Do not perform perturbative CT analysis
1
Perform perturbative CT analysis

RECOMMENDATION:

Set to 1 to perform perturbative CT analysis

EDA_SAVE_COVP

EDA_SAVE_COVP

Save significant COVPs or not

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Do not save significant COVPs
1
Save significant COVPs

RECOMMENDATION:

To save the COVPs as an fchk file, GUI = 2 also has to be set

EDA_VCT_A

EDA_VCT_A

Perform non-perturbative CT analysis

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Do not perform non-perturbative CT analysis
1
Perform non-perturbative CT analysis.

RECOMMENDATION:

Set to 1 to perform non-perturbative CT analysis

GEN_SCFMAN_EDA2

GEN_SCFMAN_EDA2

Perform ALMO-EDA calculations using the GEN_SCFMAN_EDA2 driver (differing from jobs with EDA2 $>$ 0)

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Do not use the new ALMO-EDA framework
1
Use the new ALMO-EDA framework

RECOMMENDATION:

Set to 1 to perform non-perturbative CT analysis

PLOT_ALMO_FRZ

PLOT_ALMO_FRZ

Plot ALMOs at the frozen stage of EDA2 calculations

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

FALSE
Do not plot frozen ALMOs
TRUE
Plot frozen ALMOs

RECOMMENDATION:

None

PLOT_ALMO_POL

PLOT_ALMO_POL

Plot ALMOs after the polarization calculation

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

FALSE
Do not plot polarized ALMOs
TRUE
Plot polarized ALMOs

RECOMMENDATION:

None

FDIFF_STEPSIZE

FDIFF_STEPSIZE

Displacement used for calculating derivatives by finite difference.

TYPE:

INTEGER

DEFAULT:

1
Corresponding to $1.88973\times {10}^{-5}$ a.u.

OPTIONS:

$n$
Use a step size of $n$ times the default value.

RECOMMENDATION:

Use the default unless problems arise.

RESPONSE_POLAR

RESPONSE_POLAR

Control the use of analytic or numerical polarizabilities.

TYPE:

INTEGER

DEFAULT:

0 or $-$1
= 0 for HF or DFT, $-$1 for all other methods

OPTIONS:

0
Perform an analytic polarizability calculation.
$-$1
Perform a numeric polarizability calculation even when analytic 2nd derivatives are available.

RECOMMENDATION:

None

ADC_CAP

ADC_CAP

Controls the type of CAP/ADC calculation to be performed.

TYPE:

INTEGER

DEFAULT:

0
Do not perform a CAP/ADC calculation.

OPTIONS:

1
Perform a subspace-projected CAP/ADC calculation.

RECOMMENDATION:

Set to 1 for the computation of CAP/ADC subspace projections.

ADC_CVS

ADC_CVS

Activates the use of the CVS approximation for the calculation of CVS-ADC
core-excited states.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Activates the CVS approximation.
FALSE
Do not compute core-excited states using the CVS approximation.

RECOMMENDATION:

Set to TRUE, if to obtain core-excited states for the simulation of
X-ray absorption spectra. In the case of TRUE, the *$rem* variable
CC_REST_OCC has to be defined as well.

ADC_C_C

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 the default.

ADC_C_T

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 the default.

ADC_C_X

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 the default.

ADC_DAVIDSON_CONV

ADC_DAVIDSON_CONV

Controls the convergence criterion of the Davidson procedure.

TYPE:

INTEGER

DEFAULT:

$6$
Corresponding to ${10}^{-6}$

OPTIONS:

$n\le 12$
Corresponding to ${10}^{-n}$.

RECOMMENDATION:

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

ADC_DAVIDSON_MAXITER

ADC_DAVIDSON_MAXITER

Controls the maximum number of iterations of the Davidson procedure.

TYPE:

INTEGER

DEFAULT:

60

OPTIONS:

$n$
Number of iterations

RECOMMENDATION:

Use the default unless convergence problems are encountered.

ADC_DAVIDSON_MAXSUBSPACE

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

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:

$n\le 14$
Corresponding to ${10}^{-n}$

RECOMMENDATION:

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

ADC_DENSITY_MAXITER

ADC_DENSITY_MAXITER

When setting ADC_DENSITY_ORDER = 4, this keyword controls the maximum number
of DIIS iterations carried out in the $\mathrm{\Sigma}(4+)$ procedure.

TYPE:

INTEGER

DEFAULT:

1000

OPTIONS:

$n$
User-defined integer.

RECOMMENDATION:

Use the default value.

ADC_DENSITY_ORDER

ADC_DENSITY_ORDER

Controls the order of the ground state density used for the computation of
third-order ADC matrix elements (non-CVS methods only).

TYPE:

INTEGER

DEFAULT:

2
Use strict third-order ADC(3) schemes.

OPTIONS:

3
Use a third-order ground state density computed from the IP-ADC(3)
effective transition moments and the corresponding
fourth order static self-energy according to the $\mathrm{\Sigma}(4)$ scheme
4
Use an improved third-order ground state density and the corresponding
improved fourth-order static self-energy computed according to the
self-consistent $\mathrm{\Sigma}(4+)$ procedure

RECOMMENDATION:

In case of IP-ADC(3) calculations, employing the $\mathrm{\Sigma}(4+)$ scheme
provides more accurate ionization potentials and ionized state dipole
moments.

ADC_DIIS_ECONV

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

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

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

ADC_DIIS_SIZE

Controls the size of the DIIS subspace.

TYPE:

INTEGER

DEFAULT:

7

OPTIONS:

$n$
User-defined integer

RECOMMENDATION:

None

ADC_DIIS_START

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_DIRECT

ADC_DIRECT

For third-order ADC methods, this keyword controls if some large intermediate tensor
contractions should be carried out in advance and the result saved in memory for later use
or if these quantities should be evaluated directly whenever they are encountered.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Directly evaluate some ${N}^{6}$-scaling tensor contractions. This will reduce the memory
requirement by $\sim $10 %.
FALSE
Precompute all possible ${N}^{6}$-scaling intermediates. This will speed up ADC(3)
calculations considerably (by a factor of $\sim $3 in case of ADC(3) for
$N$-electron excitations and somewhat less for IP- and EA-ADC(3)).

RECOMMENDATION:

Use the default value unless memory is the bottleneck.

ADC_DO_DIIS

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_DO_DYSON

ADC_DO_DYSON

Controls if Dyson orbitals are output in case of IP- and EA-ADC calculations. This
keyword only takes effect when used together with STATE_ANALYSIS = TRUE.
See Section. 10.2.9 for further details.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Output Dyson orbitals as cube files.
FALSE
Do not output Dyson orbitals.

RECOMMENDATION:

Set to TRUE if visualization of ionization/electron-attachment processes is
desired.

ADC_NGUESS_DOUBLES

ADC_NGUESS_DOUBLES

Controls the number of excited state guess vectors which are double excitations,
two-hole-one-particle ionizations and one-hole-two-particle electron-attachments in case
of ADC, IP-ADC and EA-ADC, respectively.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$
User-defined integer.

RECOMMENDATION:

ADC_NGUESS_SINGLES

ADC_NGUESS_SINGLES

Controls the number of excited state guess vectors which are single excitations, one-hole
ionizations and one-particle electron-attachments in case of ADC, IP-ADC and EA-ADC,
respectively. 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:

Increase if there are convergence problems.

ADC_PRINT

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
Debug: more status information, extended information on timings.
…

RECOMMENDATION:

Use the default.

ADC_PROP_ES2ES

ADC_PROP_ES2ES

Controls the calculation of transition properties between excited, ionized or
electron-attached states (currently only transition dipole moments and oscillator strengths). For ADC for
$N$-electron excitations, this keyword also controls
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, ionized or
electron-attached states.

RECOMMENDATION:

Set to TRUE, if state-to-state properties (ADC, IP-ADC, EA-ADC) or sum-over-states two-photon
absorption cross-sections (only ADC) are required.

ADC_PROP_ES

ADC_PROP_ES

Controls the calculation of excited, ionized or electron-attached state properties
(currently only dipole moments and ${\widehat{r}}^{2}$ expectation values).

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Calculate excited, ionized or electron-attached state properties.
FALSE
Do not compute state properties.

RECOMMENDATION:

Set to TRUE, if properties are required.

ADC_PROP_TPA

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.

ADC_STRICT_ISR

ADC_STRICT_ISR

Controls how second-order ground state contributions are treated in the calculation of
second- and third-order IP- and EA-ADC state properties using the second-order ISR
formalism.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Scale the second-order part of the ground state contribution to one-electron
properties of ionized/electron-attached states by the
one-hole/one-particle character of the respective states
as implied by the strict ISR derivation.
FALSE
Use the full second-order ground state contribution for each
ionized/electron-attached state property.

RECOMMENDATION:

Use the default value. Both options are, however, valid second-order treatments of
ionized/electron-attached state properties and should yield very similar results for
states with predominant one-hole/one-particle chaaracter.

ADD_CHARGED_CAGE

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.

ADIIS_INNER_CONV

ADIIS_INNER_CONV

Convergence criterion for the ADIIS inner loops (L-BFGS optimization of Eq. 4.43)

TYPE:

INTEGER

DEFAULT:

12

OPTIONS:

$n$
Using 10${}^{-n}$ as the convergence criterion for the ADIIS inner loops

RECOMMENDATION:

Use the default

AFSSH

AFSSH

Adds decoherence approximation to surface hopping calculation.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Traditional surface hopping, no decoherence.
1
Use augmented fewest-switches surface hopping (AFSSH).

RECOMMENDATION:

AFSSH will increase the cost of the calculation, but may improve accuracy
for some systems. See Refs. 1092, 1095, 620
for more detail.

AIFDEM_CTSTATES

AIFDEM_CTSTATES

Include charge-transfer-like cation/anion pair states in the AIFDEM basis.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Include CT states.
FALSE
Do not include CT states.

RECOMMENDATION:

Use if CT states are desired in the basis.

AIFDEM_EMBED_RANGE

AIFDEM_EMBED_RANGE

Specifies the size of the QM region for charge embedding

TYPE:

INTEGER

DEFAULT:

FULL_QM

OPTIONS:

FULL_QM
No charge embedding.
0
Treat only excited fragments with QM.
$n$
Range (in Å) from excited fragments within which to
treat other fragments with QM.

RECOMMENDATION:

The minimal threshold of zero typically
maintains accuracy while significantly reducing computational time.

AIFDEM_FRGM_READ

AIFDEM_FRGM_READ

Skips fragment SCF calculations.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Skips fragment SCF calculations, only computation of matrix elements.
FALSE
Regular AIFDEM calculation as specified by other *$rem* variables.

RECOMMENDATION:

Requires a prior calculation that computes fragment SCF data.

AIFDEM_FRGM_WRITE

AIFDEM_FRGM_WRITE

Fragment SCF calculations only.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Only fragment SCF calculations are carried out, no computation of matrix elements.
FALSE
Regular AIFDEM calculation as specified by other *$rem* variables.

RECOMMENDATION:

None

AIFDEM_NTOTHRESH

AIFDEM_NTOTHRESH

Controls how many NTOs that are retained in the exciton-site basis states.

TYPE:

INTEGER

DEFAULT:

99

OPTIONS:

$n$
Retain enough NTOs to recover $n$% of the norm of the original CIS or TDDFT vectors in Eq. (12.68).

RECOMMENDATION:

A threshold of $85\%$ gives a good trade-off of computational time and accuracy for organic molecules.

AIFDEM_SEGEND

AIFDEM_SEGEND

Indicates the index of the last matrix element to be computed.

TYPE:

INTEGER

DEFAULT:

NONE

OPTIONS:

$n$
Last matrix element of thhe chunk to be computed.

RECOMMENDATION:

Needs to be used with AIFDEM_SEGSTART

AIFDEM_SEGSTART

AIFDEM_SEGSTART

Indicates the index of the first matrix element to be computed.

TYPE:

INTEGER

DEFAULT:

NONE

OPTIONS:

$n$
First matrix element of the chunk to be computed.

RECOMMENDATION:

Needs to be used with AIFDEM_SEGEND

AIFDEM_SINGFIS

AIFDEM_SINGFIS

Include multi-exciton states in the AIFDEM basis.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Include multi-exciton states.
FALSE
Do not include multi-exciton states.

RECOMMENDATION:

Use if multi-exciton states are desired in the basis. This option requires the use of AIFDEM_SEGSTART and
AIFDEM_SEGEND in the *$rem* section.

AIFDEM

AIFDEM

Perform an AIFDEM calculation.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE
Do not perform an AIFDEM calculation.
TRUE
Perform an AIFDEM calculation.

RECOMMENDATION:

False

AIMD_FICT_MASS

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 Ref. 454 for examples and discussion.

AIMD_INIT_VELOC_NANO_RANDOM

AIMD_INIT_VELOC_NANO_RANDOM

Uses a more precise random seed for generating random initial velocities.

TYPE:

LOGICAL

DEFAULT:

TRUE
Use a more precise random seed.

OPTIONS:

FALSE
Use a less precise random seed.

RECOMMENDATION:

Leave this set to TRUE unless necessary.
This option determines the source of the random seed used for sampling random
initial velocities when AIMD_INIT_VELOC requires such.
Setting the option to FALSE will have the seed based on the system time in
seconds, meaning that two otherwise identical simulations starting in
the same second will produce identical initial velocities.
With the option set to TRUE, such collisions are virtually impossible.
The option is kept for legacy purposes. There should rarely ever be a need
to set it to FALSE.

AIMD_INIT_VELOC

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.
OLD
Use the same initial velocities as the immediately preceding AIMD job.
RESTART
Use the final velocities from a previous AIMD job,
reading them from disk.

RECOMMENDATION:

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

AIMD_LANGEVIN_TIMESCALE

AIMD_LANGEVIN_TIMESCALE

Sets the timescale (strength) of the Langevin thermostat

TYPE:

INTEGER

DEFAULT:

none

OPTIONS:

$n$
Thermostat timescale,asn $n$ fs

RECOMMENDATION:

Smaller values (roughly 100) equate to tighter thermostats but may inhibit
rapid sampling. Larger values ($\ge 1000$) allow for more rapid sampling but
may take longer to reach thermal equilibrium.

AIMD_METHOD

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

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

AIMD_NUCL_DACF_POINTS

Number of time points to use in the dipole auto-correlation function for an AIMD trajectory

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Do not compute dipole auto-correlation function.
$1\le n\le \text{AIMD\_STEPS}$
Compute dipole auto-correlation function for last $n$
timesteps of the trajectory.

RECOMMENDATION:

If the DACF is desired, set equal to AIMD_STEPS.

AIMD_NUCL_SAMPLE_RATE

AIMD_NUCL_SAMPLE_RATE

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

TYPE:

INTEGER

DEFAULT:

None.

OPTIONS:

$1\le n\le \text{AIMD\_STEPS}$
Update the velocity/dipole auto-correlation 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

AIMD_NUCL_VACF_POINTS

Number of time points to use in the velocity auto-correlation function for
an AIMD trajectory

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Do not compute velocity auto-correlation function.
$1\le n\le \text{AIMD\_STEPS}$
Compute velocity auto-correlation function for last $n$
time steps of the trajectory.

RECOMMENDATION:

If the VACF is desired, set equal to AIMD_STEPS.

AIMD_QCT_INITPOS

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 wave function.
$-n$
Generates $n$ random geometries sampled from
the harmonic vibrational wave function.

RECOMMENDATION:

None.

AIMD_QCT_WHICH_TRAJECTORY

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_SHORT_TIME_STEP

AIMD_SHORT_TIME_STEP

Specifies a shorter electronic time step for FSSH calculations.

TYPE:

INTEGER

DEFAULT:

TIME_STEP

OPTIONS:

$n$
Specify an electronic time step duration of $n$/AIMD_TIME_STEP_CONVERSION
a.u. If $n$ is less than the nuclear time step variable TIME_STEP, the
electronic wave function will be integrated multiple times per nuclear time step,
using a linear interpolation of nuclear quantities such as the energy gradient and
derivative coupling. Note that $n$ must divide TIME_STEP evenly.

RECOMMENDATION:

Make AIMD_SHORT_TIME_STEP as large as possible while keeping the trace of
the density matrix close to unity during long simulations. Note that while specifying an
appropriate duration for the electronic time step is essential for maintaining accurate
wave function time evolution, the electronic-only time steps employ linear interpolation
to estimate important quantities. Consequently, a short electronic time step is not a
substitute for a reasonable nuclear time step.

AIMD_STEPS

AIMD_STEPS

Specifies the requested number of molecular dynamics steps.

TYPE:

INTEGER

DEFAULT:

None.

OPTIONS:

User-specified.

RECOMMENDATION:

None.

AIMD_TEMP

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.

AIMD_THERMOSTAT

AIMD_THERMOSTAT

Applies thermostatting to AIMD trajectories.

TYPE:

INTEGER

DEFAULT:

none

OPTIONS:

LANGEVIN
Stochastic, white-noise Langevin thermostat
NOSE_HOOVER
Time-reversible, Nosé-Hoovery chain thermostat

RECOMMENDATION:

Use either thermostat for sampling the canonical (NVT) ensemble.

AIMD_TIME_STEP_CONVERSION

AIMD_TIME_STEP_CONVERSION

Modifies the molecular dynamics time step to increase granularity.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

$n$
The molecular dynamics time step is TIME_STEP/$n$ a.u.

RECOMMENDATION:

None

AIRBED_ALPHA

AIRBED_ALPHA

Sets the value of $\alpha $.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$
Corresponding to $\alpha $ = $n/1000$

RECOMMENDATION:

0 or -1200 for hBN surface

AIRBED

AIRBED

Perform an AIRBED calculation.

TYPE:

BOOLEAN

DEFAULT:

False

OPTIONS:

True
Perform an AIRBED calculation.
False
Don’t perform an AIRBED calculation.

RECOMMENDATION:

Set the *$rem* variable DFT_D to EMPIRICAL_GRIMME.

ANHAR_SEL

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

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.

ANTIBOND

ANTIBOND

Triggers Antibond subroutine to generate antibonding orbitals after a converged SCF

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Does not localize the virtual space.
1
Localizes the virtual space, one antibonding for every bond.
2,3
Fill the virtual space with antibonding orbitals-like guesses.
4
Does Frozen Natural Orbitals and leaves them on scratch for future jobs or visualization.

RECOMMENDATION:

None

ARI_R0

ARI_R0

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

TYPE:

INTEGER

DEFAULT:

4
A value of 4 Å 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

ARI_R1

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

TYPE:

INTEGER

DEFAULT:

5
A value of 5 Å 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

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.

ASCI_CDETS

ASCI_CDETS

Specifies the number of determinants to search over during ASCI wavefunction growth steps.

TYPE:

INTEGER

DEFAULT:

-5

OPTIONS:

$N>0$
search from the top $N$ determinants
$$
search from the top determinants whose cumulative weight in the wavefunction corresponds to $1-{2}^{N}$

RECOMMENDATION:

Using a dynamically determined value ($$) gives better results.

ASCI_DAVIDSON_GUESS

ASCI_DAVIDSON_GUESS

Specifies the truncated CI guess used for ASCI’s Davidson solver.

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

$N$
Order of the truncated CI to solve explicitly ASCI Davidson guess.

RECOMMENDATION:

Accurate excited states and rapid convergence of the ground state benefit from a good zero-order guess for the low energy spectrum. The default is often sufficient.

ASCI_DIAG

ASCI_DIAG

Specifies the diagonalization procedure.

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

1
Davidson solver
2
Eigen sparse matrix solver

RECOMMENDATION:

Use 2 for best trade-off of speed and memory usage. If memory usage becomes to great, switch to 1.

ASCI_NDETS

ASCI_NDETS

Specifies the number of determinants to include in the ASCI wavefunction.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$N$
for a wavefunction with $N$ determinants

RECOMMENDATION:

Typical ASCI expansions range from 50,000 to 2,000,000 determinants depending on active space size, complexity of problem, and desired accuracy

ASCI_RESTART

ASCI_RESTART

Specifies whether to initialize the ASCI wavefunction with the wf_data file.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE
read CI coefficients from the wf_data file
FALSE
do not read the CI coefficients from disk

RECOMMENDATION:

ASCI_SKIP_PT2

ASCI_SKIP_PT2

Specifies whether ASCI PT2 correction should be calculated.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

FALSE
compute ASCI PT2 contribution
TRUE
do not compute ASCI PT2 contribution

RECOMMENDATION:

The PT2 correction is essential to obtaining converged ASCI energies.

ASCI_SPIN_PURIFY

ASCI_SPIN_PURIFY

Indicates whether or not the ASCI wavefunction should be augmented with missing
determinants to ensure a spin-pure state.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE
augment the wavefunction with determinants to ensure a spin eigenstate
FALSE
do not augment the wavefunction

RECOMMENDATION:

ASCI_USE_NAT_ORBS

ASCI_USE_NAT_ORBS

Specifies whether rotation to a natural orbital basis should be carried out between growth steps.

TYPE:

BOOLEAN

DEFAULT:

TRUE

OPTIONS:

TRUE
rotate to a natural orbital basis between growth wavefunction growth steps
FALSE
do not rotate to a natural orbital basis

RECOMMENDATION:

Natural orbital rotations significantly improve the compactness and therefore accuracy of the ASCI wavefunction.

AUX_BASIS_CORR

AUX_BASIS_CORR

Sets the auxiliary basis set for RI-MP2 to be used or invokes RI-MP2 in case of double-hybrid DFT or MP2

TYPE:

STRING

DEFAULT:

No default auxiliary basis set

OPTIONS:

General, Gen
User-defined. As for BASIS
Symbol
Use standard auxiliary basis sets as in the table below
Mixed
Use a combination of different basis sets

RECOMMENDATION:

Consult literature and Basis Set Exchange to aid your selection.

AUX_BASIS_J

AUX_BASIS_J

Sets the auxiliary basis set for RI-J to be used or invokes RI-J

TYPE:

STRING

DEFAULT:

No default auxiliary basis set

OPTIONS:

General, Gen
User-defined. As for BASIS
Symbol
Use standard auxiliary basis sets as in the table below
Mixed
Use a combination of different basis sets

RECOMMENDATION:

Consult literature and Basis Set Exchange to aid your selection.

AUX_BASIS_K

AUX_BASIS_K

Sets the auxiliary basis set for RI-K or occ-RI-K to be used or invokes occ-RI-K

TYPE:

STRING

DEFAULT:

No default auxiliary basis set

OPTIONS:

General, Gen
User-defined. As for BASIS
Symbol
Use standard auxiliary basis sets as in the table below
Mixed
Use a combination of different basis sets

RECOMMENDATION:

Consult literature and Basis Set Exchange to aid your selection.

AUX_BASIS

AUX_BASIS

Sets the auxiliary basis set to be used

TYPE:

STRING

DEFAULT:

No default auxiliary basis set

OPTIONS:

General, Gen
User-defined. As for BASIS
Symbol
Use standard auxiliary basis sets as in the table below
Mixed
Use a combination of different basis sets

RECOMMENDATION:

Consult literature and Basis Set Exchange to aid your selection.

BASIS2

BASIS2

Defines the (small) second basis set.

TYPE:

STRING

DEFAULT:

No default for the second basis set.

OPTIONS:

Symbol
Use standard basis sets as for BASIS.
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
as discussed in Section 4.7 and summarized in Table 4.2.

BASISPROJTYPE

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 MOs from BASIS2 to BASIS.

RECOMMENDATION:

None

BASIS_LIN_DEP_THRESH

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

BASIS

Sets the basis set to be used

TYPE:

STRING

DEFAULT:

No default basis set

OPTIONS:

General, Gen
User-defined. See section below
Symbol
Use standard basis sets as in the table below
Mixed
Use a combination of different basis sets

RECOMMENDATION:

Consult literature and reviews to aid your selection.

BECKE_SHIFT

BECKE_SHIFT

Controls atomic cell shifting in determination of Becke weights.

TYPE:

STRING

DEFAULT:

BRAGG_SLATER

OPTIONS:

UNSHIFTED
Use Becke weighting without atomic size corrections,
based on bond midpoints.
BRAGG_SLATER
Use the empirical radii introduced by Bragg and Slater.
UNIVERSAL_DENSITY
Use the *ab initio* radii introduced by Pacios.

RECOMMENDATION:

If interested in the partitioning of the default atomic quadrature, use UNSHIFTED.
If using for physical interpretation, choose BRAGG_SLATER or UNIVERSAL_DENSITY.
All cDFT calculations and calculations where POP_BECKE = TRUE
will default to BRAGG_SLATER radii, otherwise the default grid is UNSHIFTED.

BONDED_EDA

BONDED_EDA

Use the bonded ALMO-EDA.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Do not perform bonded ALMO-EDA.
1
Perform ALMO-EDA with non-orthogonal CI.
2
Perform ALMO-EDA with spin-projected formalism.

RECOMMENDATION:

Set to 2 for all cases where the supersystem is closed shell, only use
1 for cases where the fragments have more than one unpaired spin each.

BOYSCALC

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

BOYS_CIS_NUMSTATE

Define how many states to mix with Boys localized diabatization. These states must be specified
in the *$localized_diabatization* section.

TYPE:

INTEGER

DEFAULT:

0
Do not perform Boys localized diabatization.

OPTIONS:

2 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

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

CAGE_POINTS

Defines number of point charges for the spherical cage.

TYPE:

INTEGER

DEFAULT:

100

OPTIONS:

$n$
Number of point charges to use.

RECOMMENDATION:

None

CAGE_RADIUS

CAGE_RADIUS

Defines radius of the charged cage.

TYPE:

INTEGER

DEFAULT:

225

OPTIONS:

$n$
radius is $n/100$ Å.

RECOMMENDATION:

None

CALC_NAC

CALC_NAC

Whether or not nonadiabatic couplings
will be calculated for the EOM-CC, CIS, and TDDFT wave functions.

TYPE:

INTEGER

DEFAULT:

0 (do not compute NAC)

OPTIONS:

1
NYI for EOM-CC
2
Compute NACs using Szalay’s approach (this what needs to be specified for EOM-CC).

RECOMMENDATION:

Additional response equations will be solved and gradients for all EOM states and
for summed states will be computed,
which increases the cost of calculations.
Request only when needed and do not ask for too many EOM states.

CALC_SOC

CALC_SOC

Whether or not the spin-orbit couplings between CC/EOM/ADC/CIS/TDDFT electronic states
will be calculated. In the CC/EOM-CC suite, 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. If NTO analysis is requested, analysis of spinless transition density matrices
will be performed and the spin–orbit integrals over NTO pairs will be printed.

TYPE:

INTEGER/LOGICAL

DEFAULT:

FALSE (no spin-orbit couplings will be calculated)

OPTIONS:

0/FALSE
(no spin-orbit couplings will be calculated)
1/TRUE
Activates SOC calculation. EOM-CC/EOM-MP2 only: spin-orbit couplings will be computed with the new code with L+/L- averaging
2
EOM-CC/EOM-MP2 only: spin-orbit couplings will be computed with the new code without L+/L- averaging
3
EOM-CC/EOM-MP2 only: spin-orbit couplings will be computed with the legacy code
4
One-electron spin-orbit couplings will be computed with effective nuclear charges (with L+/L- averaging
for EOM-CC/MP2)

RECOMMENDATION:

CCMAN2 supports several variants of SOC calculation for EOM-CC/EOM-MP2 methods.
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).

CALC_SOC

CALC_SOC

Controls whether to calculate the SOC constants for EOM-CC, RAS-CI, ADC, CIS, TDDFT/TDA and TDDFT/RPA.

TYPE:

INTEGER/LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE
Do not perform the SOC calculation.
TRUE
Perform the SOC calculation.

RECOMMENDATION:

Although TRUE/FALSE values will work, EOM-CC code has more variants of SOC evaluations. For details, consult with EOM section.

CAP_X_END

CAP_X_END

Controls the upper onset limit for a series of CAP onsets, where the lower limit is given
by CAP_X. The parameter value in a.u. is
obtained by multiplying the given integer by ${10}^{-3}$. Currently only used
in ADC methods.

TYPE:

INTEGER

DEFAULT:

CAP_X
Do not compute a series of CAP onsets but only use a single CAP with an
onset value of CAP_X.

OPTIONS:

$n>\text{CAP\_X}$
User-defined integer.

RECOMMENDATION:

Use this keyword if CAP onset series are desired.

CAP_X_STEP

CAP_X_STEP

Controls the step size for a series of CAP onsets between CAP_X and
CAP_X_END. The parameter value in a.u. is
obtained by multiplying the given integer by ${10}^{-3}$. Currently only used
in ADC methods.

TYPE:

INTEGER

DEFAULT:

500
corresponding to 0.5 a.u.

OPTIONS:

$n>0$
User-defined integer.

RECOMMENDATION:

None.

CAP_X

CAP_X

For ADC methods, in combination with a smoothed Voronoi-CAP
(CAP_TYPE = 2) or a spherical CAP (CAP_TYPE = 0),
this keyword controls the lower limit for a series of CAP onsets,
where the upper limit is given by CAP_X_END. The parameter value in a.u. is
obtained by multiplying the given integer by ${10}^{-3}$. In this case, the onset value defines the
region around the molecule with zero CAP strength. In combination with a
cuboid CAP (CAP_TYPE = 1) or in general for other electronic
structure methods (see 7.10.9 for further details), this keyword
controls the CAP onset in $x$ direction.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n>0$
User-defined integer.

RECOMMENDATION:

Usually, values of 2000 to 4000 (corresponding to onset values between 2.0 and 4.0 a.u.)
give reasonable results.

CAS_DAVIDSON_MAXVECTORS

CAS_DAVIDSON_MAXVECTORS

Specifies the maximum number of vectors to augment the Davidson search space in CAS.

TYPE:

INTEGER

DEFAULT:

10

OPTIONS:

$N$
sets the maximum Davidson subspace size to $N$+CAS_N_ROOTS

RECOMMENDATION:

The default should be suitable in most cases

CAS_DAVIDSON_TOL

CAS_DAVIDSON_TOL

Specifies the tolerance for the Davidson solver used in CAS.

TYPE:

INTEGER

DEFAULT:

5

OPTIONS:

$N$
for a threshold of ${10}^{-N}$

RECOMMENDATION:

The default should be suitable in most cases

CAS_DO_1X

CAS_DO_1X

Do perturbative hole (h) and particle (p) correction?

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Do perturbative hole (h) and particle (p) correction
FALSE
Do not do perturbative hole (h) and particle (p) correction

RECOMMENDATION:

None.

CAS_DO_2x

CAS_DO_2x

Do perturbative 2x (h,p,hp,hh,pp) correction?

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Do perturbative 2x correction
FALSE
Do not do perturbative 2x correction

RECOMMENDATION:

None.

CAS_DO_3x

CAS_DO_3x

Do perturbative 3x (h,p,hp,hh,pp,hhp,hpp) correction?

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Do perturbative 3x correction
FALSE
Do not do perturbative 3x correction

RECOMMENDATION:

None.

CAS_DO_DOUBLES

CAS_DO_DOUBLES

Do perturbative (h,p,hp,hh,pp,hhp,hpp) correction + MP2 RAS1->RAS3 doubles?

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Do perturbative (h,p,hp,hh,pp,hhp,hpp) + MP2 RAS1->RAS3 doubles correction
FALSE
Do not do the correction

RECOMMENDATION:

None.

CAS_DO_NDPT

CAS_DO_NDPT

Do non-degenerate perturbation theory?

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Do non-degenerate perturbation theory.
FALSE
Do not use non-degenerate perturbation theory.

RECOMMENDATION:

None.

CAS_DO_SINGLES

CAS_DO_SINGLES

Do perturbative singles (h,p,hp) correction?

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Do perturbative singles correction
FALSE
Do not do perturbative singles correction

RECOMMENDATION:

None.

CAS_LEVEL_SHIFT

CAS_LEVEL_SHIFT

Use a denominator level-shift?

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Use the denominator level-shift
FALSE
Do not use the denominator level-shift

RECOMMENDATION:

None.

CAS_LOCAL_ALGO

CAS_LOCAL_ALGO

Passed into localizer. Set to 1 if doing Boys localization.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$0$
No localization
$1$
Boys localization
$2$
Pipek-Mezey localization

RECOMMENDATION:

None.

CAS_LOCAL

CAS_LOCAL

Determines whether to do localization.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$0$
No localization
$1$
Boys localization
$2$
Pipek-Mezey localization

RECOMMENDATION:

None.

CAS_METHOD

CAS_METHOD

Indicates whether orbital optimization is requested.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Not running a CAS calculation
1
CAS-CI (no orbital optimization)
2
CASSCF (orbital optimization)

RECOMMENDATION:

Use 2 for best accuracy, but such computations may become infeasible
for large active spaces.

CAS_M_S

CAS_M_S

The number of unpaired electrons desired in the CAS wavefunction.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$N$
for a wavefunction with $N$ unpaired electrons

RECOMMENDATION:

CAS_N_ELEC

CAS_N_ELEC

Specifies the number of active electrons.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$N$
include $N$ electrons in the active space
-1
include all electrons in the active space

RECOMMENDATION:

Use the smallest active space possible for the given system.

CAS_N_ORB

CAS_N_ORB

Specifies the number of active orbitals.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$N$
include $N$ orbitals in the active space
-1
include all orbitals in the active space

RECOMMENDATION:

Use the smallest active space possible for the given system.

CAS_N_ROOTS

CAS_N_ROOTS

Specifies the number of electronic states to determine.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

$N$
solve for $N$ roots of the Hamiltonian

RECOMMENDATION:

CAS_QDPT_ORDER

CAS_QDPT_ORDER

Order of terms kept in the quasi-degenerate perturbation theory denominator expansion.

TYPE:

INTEGER

DEFAULT:

None.

OPTIONS:

$n$
Keep terms of order $n$ in the denominator expansion.

RECOMMENDATION:

None.

CAS_SAVE_NAT_ORBS

CAS_SAVE_NAT_ORBS

Save the CAS natural orbitals in place of the reference orbitals.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

TRUE
overwrite the reference orbitals with CAS natural orbitals
FALSE
do not save the CAS natural orbitals

RECOMMENDATION:

CAS_SOLVER

CAS_SOLVER

Specifies the solver to be used for the active space.

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

1
CAS-CI/CASSCF
2
ASCI (see Section 6.21)
3
Truncated CI (CIS, CISD, CISDT, etc.)

RECOMMENDATION:

CAS_SPARSE

CAS_SPARSE

Use a sparse matrix multiply when forming the effective Hamiltonian?

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Use sparse matrix multiply in forming effective Hamiltonian
FALSE
Do not use sparse matrix multiply in forming effective Hamiltonian

RECOMMENDATION:

None. Can be useful for larger numbers of spin-flips.

CAS_THRESH

CAS_THRESH

Specifies the threshold for matrix elements to be included in the CAS Hamiltonian.

TYPE:

INTEGER

DEFAULT:

12

OPTIONS:

$N$
for a threshold of ${10}^{-N}$

RECOMMENDATION:

CAS_USE_RI

CAS_USE_RI

Indicates whether the resolution of the identity approximation should be used.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

FALSE
Compute 2-electron integrals analytically
TRUE
Use the RI approximation for 2-electron integrals

RECOMMENDATION:

Analytic integrals are more accurate, RI integrals are faster

CCVB_GUESS

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 non-local 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

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_1HPOL

CC_1HPOL

Specifies the approach for calculating the first hyperpolarizability of the CCSD wave function.

TYPE:

INTEGER

DEFAULT:

0
(CCSD first hyperpolarizability will not be calculated)

OPTIONS:

1
(damped-response expectation-value approach with only first-order response wave functions)
3
(damped-response expectation-value approach with second-order response density matrices for wave-function and natural orbital analyses)

RECOMMENDATION:

CCSD first hyperpolarizabilities are expensive since they require solving a huge number of first- and second-order response equations.
Do no request this property unless you need it.

CC_BACKEND

CC_BACKEND

Used to specify the computational back-end of CCMAN2.

TYPE:

STRING

DEFAULT:

VM
Default shared-memory disk-based back-end

OPTIONS:

XM
libxm shared-memory disk-based back-end
INCORE
in-core memory back-end

RECOMMENDATION:

Use XM for large jobs with limited memory or when the performance of the
default disk-based back-end is not satisfactory, INCORE for small jobs that
fit in main memory.

CC_CANONIZE_FINAL

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

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

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

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 the default

CC_DIIS12_SWITCH

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

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

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

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

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

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

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_DIRECT_RI

CC_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.

CC_DOV_THRESH

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 $ab\times {10}^{-de}$, *e.g.*,
$2501$ corresponds to 0.025, $99001$ corresponds to 0.99, etc.

RECOMMENDATION:

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

CC_DO_DYSON_EE

CC_DO_DYSON_EE

Whether excited-state or spin-flip state Dyson orbitals will be calculated for
EOM-IP/EA-CCSD calculations with CCMAN.

TYPE:

LOGICAL

DEFAULT:

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

OPTIONS:

TRUE/FALSE

RECOMMENDATION:

none

CC_DO_DYSON

CC_DO_DYSON

CCMAN2: starts all types of Dyson orbitals calculations. Desired type is
determined by requesting corresponding EOM-XX transitions
CCMAN: whether the reference-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_FESHBACH

CC_DO_FESHBACH

Activates calculation of resonance widths using Feshbach-Fano approach.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
do not invoke Feshbach-Fano calculation
1
invoke Feshbach-Fano calculation of the resonance width
2
invoke Feshbach-Fano calculation of the resonance width and resonance shift

RECOMMENDATION:

Initial and final states should be correctly specified.

CC_EOM_2PA

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.
If 2PA NTO analysis is requested, the CC_EOM_2PA value is redundant
as long as CC_EOM_2PA $>0$.

TYPE:

INTEGER

DEFAULT:

0 (do not compute 2PA transition moments)

OPTIONS:

1
Compute 2PA using the fastest algorithm (use $\stackrel{~}{\sigma}$-intermediates for
canonical
and $\sigma $-intermediates for RI/CD response calculations).
2
Use $\sigma $-intermediates for 2PA response equation calculations.
3
Use $\stackrel{~}{\sigma}$-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 the default algorithm.
Setting CC_EOM_2PA $>0$ turns on CC_TRANS_PROP.

CC_EOM_PROP_TE

CC_EOM_PROP_TE

Request for calculation of non-relaxed two-particle EOM-CC properties. The
two-particle properties currently include $\u27e8{S}^{2}\u27e9$. 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
$\u27e8{S}^{2}\u27e9$. The variable CC_EOM_PROP must be also set to
TRUE. Alternatively, CC_CALC_SSQ can be used to
request $\u27e8{S}^{2}\u27e9$ 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.

CC_EOM_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, angular momentum projections, the second moments $\u27e8{X}^{2}\u27e9$, $\u27e8{Y}^{2}\u27e9$, and
$\u27e8{Z}^{2}\u27e9$ of electron density, and the total $\u27e8{R}^{2}\u27e9=\u27e8{X}^{2}\u27e9+\u27e8{Y}^{2}\u27e9+\u27e8{Z}^{2}\u27e9$ (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.
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 or
libwfa packages by specifying the state with CC_STATE_TO_OPT and
requesting NBO = TRUE and CC_EOM_PROP = TRUE.

CC_EOM_RIXS

CC_EOM_RIXS

Whether or not the RIXS scattering moments and cross-sections will be calculated.

TYPE:

INTEGER

DEFAULT:

0
do not compute RIXS cross-sections

OPTIONS:

1
Perform RIXS within fc-CVS-EOM-EE-CCSD using the response wave functions of the CCSD reference state only
2
Perform RIXS within fc-CVS-EOM-EE-CCSD response theory along with the wave-function analysis of RIXS transition density matrices
11
Perform RIXS within the standard EOM-EE-CCSD using the response wave functions of the CCSD reference state only
12
Use $\sigma $-intermediates for RIXS response calculations within the standard EOM-EE-CCSD

RECOMMENDATION:

Use 1 to deploy fc-CVS-EOM-EE-CCSD with robust convergence

CC_ERASE_DP_INTEGRALS

CC_ERASE_DP_INTEGRALS

Controls storage of requisite objects computed with double precision in a single-precision calculation

TYPE:

INTEGER

DEFAULT:

0
store

OPTIONS:

1
do not store

RECOMMENDATION:

Do not erase integrals if clean-up in double precision is intended.

CC_E_CONV

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_FESHBACH_CW

CC_FESHBACH_CW

Activates Coulomb wave description of the ejected electron.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Use plane wave
1
Use Coulomb wave

RECOMMENDATION:

Additional details need to be specified in *$coulomb_wave* section.

CC_FESHBACH_DELTA_INTB

CC_FESHBACH_DELTA_INTB

Specifies integration limits in calculation of energy shift in Feshbach-Fano calculations.

TYPE:

INTEGER

DEFAULT:

Preset

OPTIONS:

$n$
corresponds to energy limit in eV

RECOMMENDATION:

Use default.

CC_FESHBACH_DELTA_INTC

CC_FESHBACH_DELTA_INTC

Specifies integration limits in calculation of energy shift in Feshbach-Fano calculations.

TYPE:

INTEGER

DEFAULT:

Preset

OPTIONS:

$n$
corresponds to energy limit in eV

RECOMMENDATION:

Use default.

CC_FNO_THRESH

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

CC_FNO_USEPOP

Selection of the truncation scheme

TYPE:

INTEGER

DEFAULT:

1
OCCT

OPTIONS:

0
POVO

RECOMMENDATION:

None

CC_FULLRESPONSE

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

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

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 the 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

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

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

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

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

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${}^{\mathrm{nd}}$ order in perturbation theory.

RECOMMENDATION:

The two definitions give generally similar performance.

CC_MP2NO_GUESS

CC_MP2NO_GUESS

Will guess orbitals be natural orbitals of the MP2 wave function?
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

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_OSFNO

CC_OSFNO

Activation of OSFNO. Available only for open-shell references.

TYPE:

LOGICAL

DEFAULT:

FALSE
do not activate

OPTIONS:

TRUE
activate

RECOMMENDATION:

Use for EOM-SF-CCSD calculations from open-shell references. Available in CCMAN2 only.

CC_POL

CC_POL

Specifies the approach for calculating the polarizability of the CCSD wave function.

TYPE:

INTEGER

DEFAULT:

0
(CCSD polarizability will not be calculated)

OPTIONS:

1
(analytic-derivative or response-theory mixed symmetric-asymmetric approach)
2
(analytic-derivative or response-theory asymmetric approach)
3
(expectation-value approach with right response intermediates)
4
(expectation-value approach with left response intermediates)
13
(damped-response expectation-value approach with right response intermediates)
14
(damped-response expectation-value approach with left response intermediates)
15
(damped-response expectation-value approach with first-order response density matrices)

RECOMMENDATION:

CCSD polarizabilities are expensive since they require solving
three/six (for static) or six/twelve (for dynamical)
additional response equations. Do no request this property unless you need it.

CC_PRECONV_FZ

CC_PRECONV_FZ

In active space methods, whether to pre-converge other wave function 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

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

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

CC_PRINT

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

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

$0-7$
higher values can lead to deforestation…

RECOMMENDATION:

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

CC_QCCD_THETA_SWITCH

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

CC_REF_PROP_TE

Request for calculation of non-relaxed two-particle CCSD properties. The
two-particle properties currently include $\u27e8{S}^{2}\u27e9$. 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
$\u27e8{S}^{2}\u27e9$. 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

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 $\u27e8{X}^{2}\u27e9$, $\u27e8{Y}^{2}\u27e9$, and
$\u27e8{Z}^{2}\u27e9$ of electron density, and the total
$\u27e8{R}^{2}\u27e9=\u27e8{X}^{2}\u27e9+\u27e8{Y}^{2}\u27e9+\u27e8{Z}^{2}\u27e9$ (in atomic units).
Incompatible with JOBTYPE = FORCE, OPT, or 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 the 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 i
JOBTYPE = FORCE.

CC_RESET_THETA

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

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

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

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

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

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:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

FALSE
Do apply restrictions
TRUE
Do not apply restrictions

RECOMMENDATION:

None

CC_REST_OCC

CC_REST_OCC

Sets the number of restricted occupied orbitals including active core occupied
orbitals.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$
Restrict $n$ energetically lowest occupied orbitals to correspond to the
active core space.

RECOMMENDATION:

*Example:* cytosine with the molecular formula C${}_{4}$H${}_{5}$N${}_{3}$O
includes one oxygen atom. To calculate O 1s core-excited states, $n$ has to be
set to 1, because the 1s orbital of oxygen is the energetically lowest. To
obtain the N 1s core excitations, the integer $n$ has to be set to 4, because
the 1s orbital of the oxygen atom is included as well, since it is
energetically below the three 1s orbitals of the nitrogen atoms. Accordingly,
to simulate the C 1s spectrum of cytosine, $n$ must be set to 8.

CC_REST_TRIPLES

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

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

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_SINGLE_PREC

CC_SINGLE_PREC

Precision selection for CCSD calculation. Available in CCMAN2 only.

TYPE:

INTEGER

DEFAULT:

0
double-precision calculation

OPTIONS:

1
single-precision calculation
2
single-precision calculation followed by double-precision clean-up iterations

RECOMMENDATION:

Do not set too tight convergence thresholds when using single precision

CC_SP_DM

CC_SP_DM

Precision selection for CCSD and EOM-CCSD intermediates, density matrices, gradients, and ${S}^{2}$

TYPE:

INTEGER

DEFAULT:

0
double-precision calculation

OPTIONS:

1
single-precision calculation

RECOMMENDATION:

NONE

CC_SP_E_CONV

CC_SP_E_CONV

Energy convergence criterion in single precision in CCSD calculations.

TYPE:

INTEGER

DEFAULT:

5

OPTIONS:

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

RECOMMENDATION:

Set 6 to be consistent with the default threshold in double precision in a pure
single-precision calculation.
When used with clean-up version, it should be smaller than double-precision
threshold not to introduce extra iterations.

CC_SP_T_CONV

CC_SP_T_CONV

Amplitude convergence threshold in single precision in CCSD calculations.

TYPE:

INTEGER

DEFAULT:

3

OPTIONS:

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

RECOMMENDATION:

Set 4 to be consistent with the default threshold in double precision in a pure
single-precision run. When used with clean-up version, it should be smaller
than double-precision threshold not to introduce extra iterations.

CC_STATE_TO_OPT

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

CC_SYMMETRY

Activates point-group symmetry in the ADC calculation.

TYPE:

LOGICAL

DEFAULT:

TRUE
If the system possesses any point-group symmetry.

OPTIONS:

TRUE
Employ point-group symmetry
FALSE
Do not use point-group symmetry

RECOMMENDATION:

None

CC_THETA_CONV

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

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

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

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

CC_TRANS_PROP

Whether or not the transition dipole moment (in atomic units) and oscillator
strength and rotatory strength (in atomic units)
for the EOM-CCSD target states will be calculated. By default, the
transition dipole moment, angular momentum matrix elements,
and rotatory strengths
are calculated between the CCSD reference and the
EOM-CCSD target states. In order to calculate transition dipole moment, angular momentum matrix elements,
and rotatory strengths 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 (no transition properties will be calculated)

OPTIONS:

1 (calculate transition properties between all computed EOM state and the reference state)
2 (calculate transition properties between all pairs of EOM states)

RECOMMENDATION:

Additional equations (for the left EOM-CCSD eigenvectors plus lambda CCSD
equations in case of 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

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

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

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

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

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

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

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
${\mathbf{S}}^{-1/2}$, eigenvalues smaller than ${10}^{-\mathrm{CDFTCI}\mathrm{\_}\mathrm{SVD}\mathrm{\_}\mathrm{THRESH}}$
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

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

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 the 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_LAMBDA_MODE

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_MAXITER

CDFT_MAXITER

Maximum number of iterations for converging the constraint.

TYPE:

INTEGER

DEFAULT:

20

OPTIONS:

N
A maximum of N microiterations will be attempted.

RECOMMENDATION:

Default value is expected to be sufficient in most situations.

CDFT_POP

CDFT_POP

Sets the charge partitioning scheme for cDFT or cDFT-CI jobs.

TYPE:

STRING

DEFAULT:

BECKE

OPTIONS:

BECKE
Linear combination of atomic Becke functions
FBH
Fragment-based Hirshfeld partition

RECOMMENDATION:

None

CDFT_POSTDIIS

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 the 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

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 the 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_PRINT

CDFT_PRINT

Whether detailed information about CDFT iterations should be printed in the output file.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Print detailed information.
FALSE
Do not print detailed information.

RECOMMENDATION:

Use the default and invoke additional printing for troubleshooting.

CDFT_THRESH

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:

Default value is set to match SCF_CONVERGENCE. Use the default unless problems occur.

CDFT

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

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 6.4.1).

RECOMMENDATION:

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

CFMM_ORDER

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 the default.

CHARGE_CHARGE_REPULSION

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

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 Å.

RECOMMENDATION:

Use the default, which corresponds to the “dense grid” of Breneman and
Wiberg,^{132}, 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

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 5.5.2.

RECOMMENDATION:

None.

CHELPG_HEAD

CHELPG_HEAD

Sets the “head space”^{132} (radial extent) of the ChElPG grid.

TYPE:

INTEGER

DEFAULT:

30

OPTIONS:

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

RECOMMENDATION:

Use the default, which is the value recommended by Breneman and Wiberg.^{132}

CHELPG_H

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

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.

CHILD_MP_ORDERS

CHILD_MP_ORDERS

The multipole orders included in the prepared FERFs. The last digit specifies how many multipoles to compute,
and the digits in the front specify the multipole orders: 2: dipole (D); 3: quadrupole (Q); 4: octopole (O). Multipole
order 1 is reserved for monopole FERFs which can be used to separate the effect of orbital contraction.^{674}

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

21
D
232
DQ
2343
DQO

RECOMMENDATION:

Use 232 (DQ) when FERF is needed.

CHILD_MP

CHILD_MP

Compute FERFs for fragments and use them as the basis for SCFMI calculations.

TYPE:

BOOLEAN

DEFAULT:

FALSE

OPTIONS:

FALSE
Do not compute FERFs (use the full AO span of each fragment).
TRUE
Compute fragment FERFs.

RECOMMENDATION:

Use FERFs to compute polarization energy when large basis sets are used. In an “EDA2" calculation,
this *$rem* variable is set based on the given option automatically.

CHOLESKY_TOL

CHOLESKY_TOL

Tolerance of Cholesky decomposition of two-electron integrals

TYPE:

INTEGER

DEFAULT:

3

OPTIONS:

$n$
Corresponds to a tolerance of ${10}^{-n}$

RECOMMENDATION:

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

CISTR_PRINT

CISTR_PRINT

Controls level of output.

TYPE:

LOGICAL

DEFAULT:

FALSE
Minimal output.

OPTIONS:

TRUE
Increase output level.

RECOMMENDATION:

None

CIS_AMPL_ANAL

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_AMPL_PRINT

CIS_AMPL_PRINT

Sets the threshold for printing CIS and TDDFT excitation amplitudes.

TYPE:

INTEGER

DEFAULT:

15

OPTIONS:

$n$
Print if $|{x}_{ia}|$ or $|{y}_{ia}|$ is larger than $0.1\times n$.

RECOMMENDATION:

Use the default unless you want to see more amplitudes.

CIS_CONVERGENCE

CIS_CONVERGENCE

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

TYPE:

INTEGER

DEFAULT:

6
CIS convergence threshold 10${}^{-6}$

OPTIONS:

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

RECOMMENDATION:

None

CIS_DER_NUMSTATE

CIS_DER_NUMSTATE

Determines among how many states we calculate nonadiabatic couplings. These states must be
specified in the *$derivative_coupling* section.

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Do not calculate nonadiabatic couplings.
$n$
Calculate $n(n-1)/2$ pairs of nonadiabatic couplings.

RECOMMENDATION:

None.

CIS_DIABATH_DECOMPOSE

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 TDDFT diabatic states.

CIS_DYNAMIC_MEM

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) sufficient
to hold an array whose size grows by
$2\times OV\times {N}_{\text{roots}}$ at each CIS iteration, where ${N}_{\text{roots}}$
is the number of unconverged roots ($\le $ 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

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

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

CIS_MOMENTS

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

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE
Do not calculate excited-state moments.
TRUE
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

CIS_MULLIKEN

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

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE
Do not perform particle/hole population analysis.
TRUE
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

CIS_N_ROOTS

Sets the number of excited state roots to find

TYPE:

INTEGER

DEFAULT:

0
Do not look for any excited states

OPTIONS:

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

RECOMMENDATION:

None

CIS_RELAXED_DENSITY

CIS_RELAXED_DENSITY

Use the relaxed CIS density for attachment/detachment density analysis as well
as for for the general excited-state analysis of Section 10.2.9.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE
Do not use the relaxed CIS density in analysis.