C.4 Alphabetical Listing of $rem Variables

EDA_NOCV
       Perform the NOCV analysis and plot the significant NOCVs
TYPE:
       BOOLEAN
DEFAULT:
       FALSE
OPTIONS:
       FALSE Do not perform NOCV analysis TRUE Perform NOCV analysis
RECOMMENDATION:
       None

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
       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

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

LOCAL_CIS
       Invoke ALMO-CIS/ALMO-CIS+CT.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Regular CIS 1 ALMO-CIS/ALMO-CIS+CT without RI(slow) 2 ALMO-CIS/ALMO-CIS+CT with RI
RECOMMENDATION:
       2 if ALMO-CIS is desired.

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.⁵⁵

NN_THRESH
       The distance cutoff for neighboring fragments (between which CT is enabled).
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Do not include interfragment transitions (ALMO-CIS). $n$ Include interfragment excitations between pairs of fragments the distances between whom are smaller than $n$ Bohr (ALMO-CIS+CT).
RECOMMENDATION:
       None

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 given by SCF_SAVEMINIMA = $n$. 4 Generate all CAS excitations from each reference determinant, where the active orbitals are specified using $active_orbitals.
RECOMMENDATION:
       By default, these multiple determinants are optimized at the SCF level before running NOCI. This behaviour can be turned off using by specifying SKIP_SCFMAN = TRUE.

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
       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 the $scf_read keyword.

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
       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
       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.

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.

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 ALMOs after the polarization calculation
TYPE:
       BOOLEAN
DEFAULT:
       FALSE
OPTIONS:
       FALSE Do not plot polarized ALMOs TRUE Plot polarized ALMOs
RECOMMENDATION:
       None

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
       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_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
       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
       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
       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
       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
       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
       Controls the maximum subspace size for the Davidson procedure.
TYPE:
       INTEGER
DEFAULT:
       $5\times$ the number of excited states to be calculated.
OPTIONS:
       $n$ User-defined integer.
RECOMMENDATION:
       Should be at least $2-4\times$ the number of excited states to calculate. The larger the value the more disk space is required.

ADC_DAVIDSON_THRESH
       Controls the threshold for the norm of expansion vectors to be added during the Davidson procedure.
TYPE:
       INTEGER
DEFAULT:
       Twice the value of ADC_DAVIDSON_CONV, but at maximum ${10}^{-14}$.
OPTIONS:
       $n\le 14$ 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_DIIS_ECONV
       Controls the convergence criterion for the excited state energy during DIIS.
TYPE:
       INTEGER
DEFAULT:
       6 Corresponding to ${10}^{-6}$
OPTIONS:
       $n$ Corresponding to ${10}^{-n}$
RECOMMENDATION:
       None

ADC_DIIS_MAXITER
       Controls the maximum number of DIIS iterations.
TYPE:
       INTEGER
DEFAULT:
       50
OPTIONS:
       $n$ User-defined integer.
RECOMMENDATION:
       Increase in case of slow convergence.

ADC_DIIS_RCONV
       Convergence criterion for the residual vector norm of the excited state during DIIS.
TYPE:
       INTEGER
DEFAULT:
       6 Corresponding to ${10}^{-6}$
OPTIONS:
       $n$ Corresponding to ${10}^{-n}$
RECOMMENDATION:
       None

ADC_DIIS_SIZE
       Controls the size of the DIIS subspace.
TYPE:
       INTEGER
DEFAULT:
       7
OPTIONS:
       $n$ User-defined integer
RECOMMENDATION:
       None

ADC_DIIS_START
       Controls the iteration step at which DIIS is turned on.
TYPE:
       INTEGER
DEFAULT:
       1
OPTIONS:
       $n$ User-defined integer.
RECOMMENDATION:
       Set to a large number to switch off DIIS steps.

ADC_DO_DIIS
       Activates the use of the DIIS algorithm for the calculation of ADC(2) excited states.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       TRUE Use DIIS algorithm. FALSE Do diagonalization using Davidson algorithm.
RECOMMENDATION:
       None.

ADC_NGUESS_DOUBLES
       Controls the number of excited state guess vectors which are double excitations.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       $n$ User-defined integer.
RECOMMENDATION:
      

ADC_NGUESS_SINGLES
       Controls the number of excited state guess vectors which are single excitations. If the number of requested excited states exceeds the total number of guess vectors (singles and doubles), this parameter is automatically adjusted, so that the number of guess vectors matches the number of requested excited states.
TYPE:
       INTEGER
DEFAULT:
       Equals to the number of excited states requested.
OPTIONS:
       $n$ User-defined integer.
RECOMMENDATION:
      

ADC_PRINT
       Controls the amount of printing during an ADC calculation.
TYPE:
       INTEGER
DEFAULT:
       1 Basic status information and results are printed.
OPTIONS:
       0 Quiet: almost only results are printed. 1 Normal: basic status information and results are printed. 2 Debug: more status information, extended information on timings. …
RECOMMENDATION:
       Use the default.

ADC_PROP_ES2ES
       Controls the calculation of transition properties between excited states (currently only transition dipole moments and oscillator strengths), as well as the computation of two-photon absorption cross-sections of excited states using the sum-over-states expression.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       TRUE Calculate state-to-state transition properties. FALSE Do not compute transition properties between excited states.
RECOMMENDATION:
       Set to TRUE, if state-to-state properties or sum-over-states two-photon absorption cross-sections are required.

ADC_PROP_ES
       Controls the calculation of excited state properties (currently only dipole moments).
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       TRUE Calculate excited state properties. FALSE Do not compute state properties.
RECOMMENDATION:
       Set to TRUE, if properties are required.

ADC_PROP_TPA
       Controls the calculation of two-photon absorption cross-sections of excited states using matrix inversion techniques.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       TRUE Calculate two-photon absorption cross-sections. FALSE Do not compute two-photon absorption cross-sections.
RECOMMENDATION:
       Set to TRUE, if to obtain two-photon absorption cross-sections.

ADD_CHARGED_CAGE
       Add a point charge cage of a given radius and total charge.
TYPE:
       INTEGER
DEFAULT:
       0 No cage.
OPTIONS:
       0 No cage. 1 Dodecahedral cage. 2 Spherical cage.
RECOMMENDATION:
       Spherical cage is expected to yield more accurate results, especially for small radii.

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.  894, 897, 519 for more detail.

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:
       None

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 Å typically maintains accuracy while significantly reducing computational time.

AIFDEM_NTOTHRESH
       Controls the number of NTOs that are retained in the exciton-site basis states.
TYPE:
       INTEGER
DEFAULT:
       99
OPTIONS:
       $n$ Threshold percentage of the norm of fragment NTO amplitudes.
RECOMMENDATION:
       A threshold of $85\%$ gives a good trade-off of computational time and accuracy for organic molecules.

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
       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. 370 for examples and discussion.

AIMD_INIT_VELOC
       Specifies the method for selecting initial nuclear velocities.
TYPE:
       STRING
DEFAULT:
       None
OPTIONS:
       THERMAL Random sampling of nuclear velocities from a Maxwell-Boltzmann distribution. The user must specify the temperature in Kelvin via the $rem variable AIMD_TEMP. ZPE Choose velocities in order to put zero-point vibrational energy into each normal mode, with random signs. This option requires that a frequency job to be run beforehand. QUASICLASSICAL Puts vibrational energy into each normal mode. In contrast to the ZPE option, here the vibrational energies are sampled from a Boltzmann distribution at the desired simulation temperature. This also triggers several other options, as described below.
RECOMMENDATION:
       This variable need only be specified in the event that velocities are not specified explicitly in a $velocity section.

AIMD_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
       Selects an ab initio molecular dynamics algorithm.
TYPE:
       STRING
DEFAULT:
       BOMD
OPTIONS:
       BOMD Born-Oppenheimer molecular dynamics. CURVY Curvy-steps Extended Lagrangian molecular dynamics.
RECOMMENDATION:
       BOMD yields exact classical molecular dynamics, provided that the energy is tolerably conserved. ELMD is an approximation to exact classical dynamics whose validity should be tested for the properties of interest.

AIMD_MOMENTS
       Requests that multipole moments be output at each time step.
TYPE:
       INTEGER
DEFAULT:
       0 Do not output multipole moments.
OPTIONS:
       $n$ Output the first $n$ multipole moments.
RECOMMENDATION:
       None

AIMD_NUCL_DACF_POINTS
       Number of time points to 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
       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
       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
       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
       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
       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
       Specifies the requested number of molecular dynamics steps.
TYPE:
       INTEGER
DEFAULT:
       None.
OPTIONS:
       User-specified.
RECOMMENDATION:
       None.

AIMD_TEMP
       Specifies a temperature (in Kelvin) for Maxwell-Boltzmann velocity sampling.
TYPE:
       INTEGER
DEFAULT:
       None
OPTIONS:
       User-specified number of Kelvin.
RECOMMENDATION:
       This variable is only useful in conjunction with AIMD_INIT_VELOC = THERMAL. Note that the simulations are run at constant energy, rather than constant temperature, so the mean nuclear kinetic energy will fluctuate in the course of the simulation.

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
       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

ANHAR_SEL
       Select a subset of normal modes for subsequent anharmonic frequency analysis.
TYPE:
       LOGICAL
DEFAULT:
       FALSE Use all normal modes
OPTIONS:
       TRUE Select subset of normal modes
RECOMMENDATION:
       None

ANHAR
       Performing various nuclear vibrational theory (TOSH, VPT2, VCI) calculations to obtain vibrational anharmonic frequencies.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       TRUE Carry out the anharmonic frequency calculation. FALSE Do harmonic frequency calculation.
RECOMMENDATION:
       Since this calculation involves the third and fourth derivatives at the minimum of the potential energy surface, it is recommended that the GEOM_OPT_TOL_DISPLACEMENT, GEOM_OPT_TOL_GRADIENT and GEOM_OPT_TOL_ENERGY tolerances are set tighter. Note that VPT2 calculations may fail if the system involves accidental degenerate resonances. See the VCI $rem variable for more details about increasing the accuracy of anharmonic calculations.

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
       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
       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
       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
       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
       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
       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
       Specifies whether to initialize the ASCI wavefunction with the “wf_data” file.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       1 read CI coefficients from the “wf_data” file 0 do not read the CI coefficients from disk
RECOMMENDATION:
      

ASCI_SKIP_PT2
       Specifies whether ASCI PT2 correction should be calculated.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 compute ASCI PT2 contribution 1 do not compute ASCI PT2 contribution
RECOMMENDATION:
       The PT2 correction is essential to obtaining converged ASCI energies.

ASCI_SPIN_PURIFY
       Indicates whether or not the ASCI wavefunction should be augmented with missing determinants to ensure a spin-pure stae.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       1 augment the wavefunction with determinants to ensure a spin eigenstate 0 do not augment the wavefunction
RECOMMENDATION:
      

ASCI_USE_NAT_ORBS
       Specifies whether rotation to a natural orbital basis should be carried out between growth steps.
TYPE:
       INTEGER
DEFAULT:
       1
OPTIONS:
       1 rotate to a natural orbital basis between growth wavefunction growth steps 0 do not rotate to a natural orbital basis
RECOMMENDATION:
       Natural orbital rotations signficantly improve the compactness and therefore accuracy of the ASCI wavefunction.

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 EMSL Basis Set Exchange to aid your selection.

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 EMSL Basis Set Exchange to aid your selection.

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 EMSL Basis Set Exchange to aid your selection.

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 EMSL Basis Set Exchange to aid your selection.

BASIS2
       Sets the small basis set to use in basis set projection.
TYPE:
       STRING
DEFAULT:
       No second basis set default.
OPTIONS:
       Symbol. Use standard basis sets as per Chapter 8. BASIS2_GEN General BASIS2 BASIS2_MIXED Mixed BASIS2
RECOMMENDATION:
       BASIS2 should be smaller than BASIS. There is little advantage to using a basis larger than a minimal basis when BASIS2 is used for initial guess purposes. Larger, standardized BASIS2 options are available for dual-basis calculations (see Section 4.7).

BASISPROJTYPE
       Determines which method to use when projecting the density matrix of BASIS2
TYPE:
       STRING
DEFAULT:
       FOPPROJECTION (when DUAL_BASIS_ENERGY=false) OVPROJECTION (when DUAL_BASIS_ENERGY=true)
OPTIONS:
       FOPPROJECTION Construct the Fock matrix in the second basis OVPROJECTION Projects MOs from BASIS2 to BASIS.
RECOMMENDATION:
       None

BASIS_LIN_DEP_THRESH
       Sets the threshold for determining linear dependence in the basis set
TYPE:
       INTEGER
DEFAULT:
       6 Corresponding to a threshold of ${10}^{-6}$
OPTIONS:
       $n$ Sets the threshold to ${10}^{-n}$
RECOMMENDATION:
       Set to 5 or smaller if you have a poorly behaved SCF and you suspect linear dependence in you basis set. Lower values (larger thresholds) may affect the accuracy of the calculation.

BASIS
       Specifies the basis sets to be used.
TYPE:
       STRING
DEFAULT:
       No default basis set
OPTIONS:
       General, Gen User defined ($basis keyword required). Symbol Use standard basis sets as per Chapter 8. Mixed Use a mixture of basis sets (see Chapter 8).
RECOMMENDATION:
       Consult literature and reviews to aid your selection.

BECKE_SHIFT
       Controls atomic cell shifting in determination of Becke weights.
TYPE:
       STRING
DEFAULT:
       UNSHIFTED
OPTIONS:
       UNSHIFTED Use the original weighting scheme of Becke (bisection point). BRAGG_SLATER Use the empirically derived Bragg-Slater radii. UNIVERSAL_DENSITY Use the ab initio derived Pacios radii.
RECOMMENDATION:
       If interested in the partitioning of the default atomic quadrature, use UNSHIFTED. If using for physical interpretation, choose BRAGG_SLATER or UNIVERSAL_DENSITY.

BOYSCALC
       Specifies the Boys localized orbitals are to be calculated
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Do not perform localize the occupied space. 1 Allow core-valence mixing in Boys localization. 2 Localize core and valence separately.
RECOMMENDATION:
       None

BOYS_CIS_NUMSTATE
       Define how many states to mix with Boys localized diabatization. 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
       Defines the total charge of the cage.
TYPE:
       INTEGER
DEFAULT:
       400 Add a cage charged +4e.
OPTIONS:
       $n$ Total charge of the cage is $n/100$ a.u.
RECOMMENDATION:
       None

CAGE_POINTS
       Defines number of point charges for the spherical cage.
TYPE:
       INTEGER
DEFAULT:
       100
OPTIONS:
       $n$ Number of point charges to use.
RECOMMENDATION:
       None

CAGE_RADIUS
       Defines radius of the charged cage.
TYPE:
       INTEGER
DEFAULT:
       225
OPTIONS:
       $n$ radius is $n/100$ Å.
RECOMMENDATION:
       None

CALC_NAC
       Whether or not non-adiabatic 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
       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
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
       Controls whether to calculate the SOC constants for EOM-CC, ADC, TDDFT/TDA and TDDFT.
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.

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
       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_METHOD
       Indicates whether orbital optimization is requested.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       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
       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
       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
       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
       Specifies the number of electronic states to determine.
TYPE:
       INTEGER
DEFAULT:
       1
OPTIONS:
       $N$ solve for $N$ roots of the Hamiltonian
RECOMMENDATION:
      

CAS_SAVE_NAT_ORBS
       Save the CAS natural orbitals in place of the reference orbitals.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       1 overwrite the reference orbitals with CAS natural orbitals 0 do not save the CAS natural orbitals
RECOMMENDATION:
      

CAS_SOLVER
       Specifies the solver to be used for the active space.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       1 CAS-CI/CASSCF 2 ASCI (see Section LABEL:sec:asci) 3 Truncated CI (CIS, CISD, CISDT, etc.)
RECOMMENDATION:
      

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
       Indicates whether the resolution of the identity approximation should be used.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Compute 2-electron integrals analytically 1 Use the RI approximation for 2-electron integrals
RECOMMENDATION:
       Analytic integrals are more accurate, RI integrals are faster

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
       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_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 CTF Distributed-memory back-end for MPI jobs
RECOMMENDATION:
       Use XM for large jobs with limited memory or when the performance of the default disk-based back-end is not satisfactory, CTF for MPI jobs

CC_CANONIZE_FINAL
       Whether to semi-canonicalize orbitals at the end of the ground state calculation.
TYPE:
       LOGICAL
DEFAULT:
       FALSE unless required
OPTIONS:
       TRUE/FALSE
RECOMMENDATION:
       Should not normally have to be altered.

CC_CANONIZE_FREQ
       The orbitals will be semi-canonicalized every $n$ theta resets. The thetas (orbital rotation angles) are reset every CC_RESET_THETA iterations. The counting of iterations differs for active space (VOD, VQCCD) calculations, where the orbitals are always canonicalized at the first theta-reset.
TYPE:
       INTEGER
DEFAULT:
       50
OPTIONS:
       $n$ User-defined integer
RECOMMENDATION:
       Smaller values can be tried in cases that do not converge.

CC_CANONIZE
       Whether to semi-canonicalize orbitals at the start of the calculation (i.e. Fock matrix is diagonalized in each orbital subspace)
TYPE:
       LOGICAL
DEFAULT:
       TRUE
OPTIONS:
       TRUE/FALSE
RECOMMENDATION:
       Should not normally have to be altered.

CC_CONVERGENCE
       Overall convergence criterion for the coupled-cluster codes. This is designed to ensure at least $n$ significant digits in the calculated energy, and automatically sets the other convergence-related variables (CC_E_CONV, CC_T_CONV, CC_THETA_CONV, CC_THETA_GRAD_CONV) [${10}^{-n}$].
TYPE:
       INTEGER
DEFAULT:
       6 Energies. 7 Gradients.
OPTIONS:
       $n$ Corresponding to ${10}^{-n}$ convergence criterion. Amplitude convergence is set automatically to match energy convergence.
RECOMMENDATION:
       Use the default

CC_DIIS12_SWITCH
       When to switch from DIIS2 to DIIS1 procedure, or when DIIS2 procedure is required to generate DIIS guesses less frequently. Total value of DIIS error vector must be less than ${10}^{-n}$, where $n$ is the value of this option.
TYPE:
       INTEGER
DEFAULT:
       5
OPTIONS:
       $n$ User-defined integer
RECOMMENDATION:
       None

CC_DIIS_FREQ
       DIIS extrapolation will be attempted every n iterations. However, DIIS2 will be attempted every iteration while total error vector exceeds CC_DIIS12_SWITCH. DIIS1 cannot generate guesses more frequently than every 2 iterations.
TYPE:
       INTEGER
DEFAULT:
       2
OPTIONS:
       $N$ User-defined integer
RECOMMENDATION:
       None

CC_DIIS_MAX_OVERLAP
       DIIS extrapolations will not begin until square root of the maximum element of the error overlap matrix drops below this value.
TYPE:
       DOUBLE
DEFAULT:
       100 Corresponding to 1.0
OPTIONS:
       $abcde$ Integer code is mapped to $abc\times {10}^{-de}$
RECOMMENDATION:
       None

CC_DIIS_MIN_OVERLAP
       The DIIS procedure will be halted when the square root of smallest element of the error overlap matrix is less than ${10}^{-n}$, where $n$ is the value of this option. Small values of the B matrix mean it will become near-singular, making the DIIS equations difficult to solve.
TYPE:
       INTEGER
DEFAULT:
       11
OPTIONS:
       $n$ User-defined integer
RECOMMENDATION:
       None

CC_DIIS_SIZE
       Specifies the maximum size of the DIIS space.
TYPE:
       INTEGER
DEFAULT:
       7
OPTIONS:
       $n$ User-defined integer
RECOMMENDATION:
       Larger values involve larger amounts of disk storage.

CC_DIIS_START
       Iteration number when DIIS is turned on. Set to a large number to disable DIIS.
TYPE:
       INTEGER
DEFAULT:
       3
OPTIONS:
       $n$ User-defined
RECOMMENDATION:
       Occasionally DIIS can cause optimized orbital coupled-cluster calculations to diverge through large orbital changes. If this is seen, DIIS should be disabled.

CC_DIIS
       Specify the version of Pulay’s Direct Inversion of the Iterative Subspace (DIIS) convergence accelerator to be used in the coupled-cluster code.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Activates procedure 2 initially, and procedure 1 when gradients are smaller than DIIS12_SWITCH. 1 Uses error vectors defined as differences between parameter vectors from successive iterations. Most efficient near convergence. 2 Error vectors are defined as gradients scaled by square root of the approximate diagonal Hessian. Most efficient far from convergence.
RECOMMENDATION:
       DIIS1 can be more stable. If DIIS problems are encountered in the early stages of a calculation (when gradients are large) try DIIS1.

CC_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
       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
       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
       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_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 $\tilde{\sigma }$-intermediates for canonical and $\sigma$-intermediates for RI/CD response calculations). 2 Use $\sigma$-intermediates for 2PA response equation calculations. 3 Use $\tilde{\sigma }$-intermediates for 2PA response equation calculations.
RECOMMENDATION:
       Additional response equations (6 for each target state) will be solved, which increases the cost of calculations. The cost of 2PA moments is about 10 times that of energy calculation. Use the default algorithm. Setting CC_EOM_2PA $>0$ turns on CC_TRANS_PROP.

CC_EOM_PROP_TE
       Request for calculation of non-relaxed two-particle EOM-CC properties. The two-particle properties currently include $⟨S^2⟩$. 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 $⟨S^2⟩$. The variable CC_EOM_PROP must be also set to TRUE. Alternatively, CC_CALC_SSQ can be used to request $⟨S^2⟩$ 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
       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 $⟨X^2⟩$, $⟨Y^2⟩$, and $⟨Z^2⟩$ of electron density, and the total $⟨R^2⟩=⟨X^2⟩+⟨Y^2⟩+⟨Z^2⟩$ (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
       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 the fc-CVS-EOM-EE-CCSD using the response wave functions of the CCSD reference state only 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
       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
       Convergence desired on the change in total energy, between iterations.
TYPE:
       INTEGER
DEFAULT:
       10
OPTIONS:
       $n$ ${10}^{-n}$ convergence criterion.
RECOMMENDATION:
       None

CC_FNO_THRESH
       Initialize the FNO truncation and sets the threshold to be used for both cutoffs (OCCT and POVO)
TYPE:
       INTEGER
DEFAULT:
       None
OPTIONS:
       range 0000-10000 $abcd$ Corresponding to $ab.cd$%
RECOMMENDATION:
       None

CC_FNO_USEPOP
       Selection of the truncation scheme
TYPE:
       INTEGER
DEFAULT:
       1 OCCT
OPTIONS:
       0 POVO
RECOMMENDATION:
       None

CC_FULLRESPONSE
       Fully relaxed properties (including orbital relaxation terms) will be computed. The variable CC_REF_PROP must be also set to TRUE.
TYPE:
       LOGICAL
DEFAULT:
       FALSE (no orbital response will be calculated)
OPTIONS:
       FALSE, TRUE
RECOMMENDATION:
       Not available for non UHF/RHF references and for the methods that do not have analytic gradients (e.g., QCISD).

CC_HESS_THRESH
       Minimum allowed value for the orbital Hessian. Smaller values are replaced by this constant.
TYPE:
       DOUBLE
DEFAULT:
       102 Corresponding to 0.01
OPTIONS:
       $abcde$ Integer code is mapped to $abc\times {10}^{-de}$
RECOMMENDATION:
       None

CC_INCL_CORE_CORR
       Whether to include the correlation contribution from frozen core orbitals in non iterative (2) corrections, such as OD(2) and CCSD(2).
TYPE:
       LOGICAL
DEFAULT:
       TRUE
OPTIONS:
       TRUE FALSE
RECOMMENDATION:
       Use 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
       In active space calculations, use a “mixed” iteration procedure if the value is greater than 0. Then if the RMS orbital gradient is larger than the value of CC_THETA_GRAD_THRESH, micro-iterations will be performed to converge the occupied-virtual mixing angles for the current active space. The maximum number of space iterations is given by this option.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       $n$ Up to $n$ occupied-virtual iterations per overall cycle
RECOMMENDATION:
       Can be useful for non-convergent active space calculations

CC_ITERATE_OV
       In active space calculations, use a “mixed” iteration procedure if the value is greater than 0. Then, if the RMS orbital gradient is larger than the value of CC_THETA_GRAD_THRESH, micro-iterations will be performed to converge the occupied-virtual mixing angles for the current active space. The maximum number of such iterations is given by this option.
TYPE:
       INTEGER
DEFAULT:
       0 No “mixed” iterations
OPTIONS:
       $n$ Up to $n$ occupied-virtual iterations per overall cycle
RECOMMENDATION:
       Can be useful for non-convergent active space calculations.

CC_MAX_ITER
       Maximum number of iterations to optimize the coupled-cluster energy.
TYPE:
       INTEGER
DEFAULT:
       200
OPTIONS:
       $n$ up to $n$ iterations to achieve convergence.
RECOMMENDATION:
       None

CC_MEMORY
       Specifies the maximum size, in MB, of the buffers for in-core storage of block-tensors in CCMAN and CCMAN2.
TYPE:
       INTEGER
DEFAULT:
       50% of MEM_TOTAL. If MEM_TOTAL is not set, use 1.5 GB. A minimum of 192 MB is hard-coded.
OPTIONS:
       $n$ Integer number of MB
RECOMMENDATION:
       Larger values can give better I/O performance and are recommended for systems with large memory (add to your .qchemrc file. When running CCMAN2 exclusively on a node, CC_MEMORY should be set to 75–80% of the total available RAM. )

CC_MP2NO_GRAD
       If CC_MP2NO_GUESS is TRUE, what kind of one-particle density matrix is used to make the guess orbitals?
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       TRUE 1 PDM from MP2 gradient theory. FALSE 1 PDM expanded to 2${}^{\mathrm{nd}}$ order in perturbation theory.
RECOMMENDATION:
       The two definitions give generally similar performance.

CC_MP2NO_GUESS
       Will guess orbitals be natural orbitals of the MP2 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
       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_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)
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
       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
       Whether to pre-converge the cluster amplitudes before each change of the orbitals in optimized orbital coupled-cluster methods. The maximum number of iterations in this pre-convergence procedure is given by the value of this parameter.
TYPE:
       INTEGER
DEFAULT:
       0 (FALSE)
OPTIONS:
       0 No pre-convergence before orbital optimization. $n$ Up to $n$ iterations in this pre-convergence procedure.
RECOMMENDATION:
       A very slow last resort option for jobs that do not converge.

CC_PRECONV_T2Z
       Whether to pre-converge the cluster amplitudes before beginning orbital optimization in optimized orbital cluster methods.
TYPE:
       INTEGER
DEFAULT:
       0 (FALSE) 10 If CC_RESTART, CC_RESTART_NO_SCF or CC_MP2NO_GUESS are TRUE
OPTIONS:
       0 No pre-convergence before orbital optimization. $n$ Up to $n$ iterations in this pre-convergence procedure.
RECOMMENDATION:
       Experiment with this option in cases of convergence failure.

CC_PRINT
       Controls the output from post-MP2 coupled-cluster module of Q-Chem
TYPE:
       INTEGER
DEFAULT:
       1
OPTIONS:
       $0-7$ higher values can lead to deforestation…
RECOMMENDATION:
       Increase if you need more output and don’t like trees

CC_QCCD_THETA_SWITCH
       QCCD calculations switch from OD to QCCD when the rotation gradient is below this threshold [${10}^{-n}$]
TYPE:
       INTEGER
DEFAULT:
       2 ${10}^{-2}$ switchover
OPTIONS:
       $n$ ${10}^{-n}$ switchover
RECOMMENDATION:
       None

CC_REF_PROP_TE
       Request for calculation of non-relaxed two-particle CCSD properties. The two-particle properties currently include $⟨S^2⟩$. 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 $⟨S^2⟩$. The variable CC_REF_PROP must be also set to TRUE.
TYPE:
       LOGICAL
DEFAULT:
       FALSE (no two-particle properties will be calculated)
OPTIONS:
       FALSE, TRUE
RECOMMENDATION:
       The two-particle properties are computationally expensive, since they require calculation and use of the two-particle density matrix (the cost is approximately the same as the cost of an analytic gradient calculation). Do not request the two-particle properties unless you really need them.

CC_REF_PROP
       Whether or not the non-relaxed (expectation value) or full response (including orbital relaxation terms) one-particle CCSD properties will be calculated. The properties currently include permanent dipole moment, the second moments $⟨X^2⟩$, $⟨Y^2⟩$, and $⟨Z^2⟩$ of electron density, and the total $⟨R^2⟩=⟨X^2⟩+⟨Y^2⟩+⟨Z^2⟩$ (in atomic units). Incompatible with JOBTYPE=FORCE, OPT, FREQ.
TYPE:
       LOGICAL
DEFAULT:
       FALSE (no one-particle properties will be calculated)
OPTIONS:
       FALSE, TRUE
RECOMMENDATION:
       Additional equations need to be solved (lambda CCSD equations) for properties with the cost approximately the same as CCSD equations. Use 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 JOBTYPE=FORCE.

CC_RESET_THETA
       The reference MO coefficient matrix is reset every n iterations to help overcome problems associated with the theta metric as theta becomes large.
TYPE:
       INTEGER
DEFAULT:
       15
OPTIONS:
       $n$ $n$ iterations between resetting orbital rotations to zero.
RECOMMENDATION:
       None

CC_RESTART_NO_SCF
       Should an optimized orbital coupled cluster calculation begin with optimized orbitals from a previous calculation? When TRUE, molecular orbitals are initially orthogonalized, and CC_PRECONV_T2Z and CC_CANONIZE are set to TRUE while other guess options are set to FALSE
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       TRUE/FALSE
RECOMMENDATION:
       None

CC_RESTART
       Allows an optimized orbital coupled cluster calculation to begin with an initial guess for the orbital transformation matrix U other than the unit vector. The scratch file from a previous run must be available for the U matrix to be read successfully.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       FALSE Use unit initial guess. TRUE Activates CC_PRECONV_T2Z, CC_CANONIZE, and turns off CC_MP2NO_GUESS
RECOMMENDATION:
       Useful for restarting a job that did not converge, if files were saved.

CC_RESTR_AMPL
       Controls the restriction on amplitudes is there are restricted orbitals
TYPE:
       INTEGER
DEFAULT:
       1
OPTIONS:
       0 All amplitudes are in the full space 1 Amplitudes are restricted, if there are restricted orbitals
RECOMMENDATION:
       None

CC_RESTR_TRIPLES
       Controls which space the triples correction is computed in
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Triples are computed in the full space 1 Triples are restricted to the active space
RECOMMENDATION:
       None

CC_REST_AMPL
       Forces the integrals, $T$, and $R$ amplitudes to be determined in the full space even though the CC_REST_OCC and CC_REST_VIR keywords are used.
TYPE:
       LOGICAL
DEFAULT:
       TRUE
OPTIONS:
       FALSE Do apply restrictions TRUE Do not apply restrictions
RECOMMENDATION:
       None

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
       Restricts $R_3$ amplitudes to the active space, i.e., one electron should be removed from the active occupied orbital and one electron should be added to the active virtual orbital.
TYPE:
       INTEGER
DEFAULT:
       1
OPTIONS:
       1 Applies the restrictions
RECOMMENDATION:
       None

CC_REST_VIR
       Sets the number of restricted virtual orbitals including frozen virtual orbitals.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       $n$ Restrict $n$ virtual orbitals.
RECOMMENDATION:
       None

CC_SCALE_AMP
       If not 0, scales down the step for updating coupled-cluster amplitudes in cases of problematic convergence.
TYPE:
       INTEGER
DEFAULT:
       0 no scaling
OPTIONS:
       $abcd$ Integer code is mapped to $abcd\times {10}^{-2}$, e.g., $90$ corresponds to 0.9
RECOMMENDATION:
       Use 0.9 or 0.8 for non convergent coupled-cluster calculations.

CC_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
       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
       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
       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
       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
       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
       Convergence criterion on the RMS difference between successive sets of orbital rotation angles [${10}^{-n}$].
TYPE:
       INTEGER
DEFAULT:
       5 Energies 6 Gradients
OPTIONS:
       $n$ ${10}^{-n}$ convergence criterion.
RECOMMENDATION:
       Use default

CC_THETA_GRAD_CONV
       Convergence desired on the RMS gradient of the energy with respect to orbital rotation angles [${10}^{-n}$].
TYPE:
       INTEGER
DEFAULT:
       7 Energies 8 Gradients
OPTIONS:
       $n$ ${10}^{-n}$ convergence criterion.
RECOMMENDATION:
       Use default

CC_THETA_GRAD_THRESH
       RMS orbital gradient threshold [${10}^{-n}$] above which “mixed iterations” are performed in active space calculations if CC_ITERATE_OV is TRUE.
TYPE:
       INTEGER
DEFAULT:
       2
OPTIONS:
       $n$ ${10}^{-n}$ threshold.
RECOMMENDATION:
       Can be made smaller if convergence difficulties are encountered.

CC_THETA_STEPSIZE
       Scale factor for the orbital rotation step size. The optimal rotation steps should be approximately equal to the gradient vector.
TYPE:
       INTEGER
DEFAULT:
       $100$ Corresponding to 1.0
OPTIONS:
       $abcde$ Integer code is mapped to $abc\times {10}^{-de}$ If the initial step is smaller than 0.5, the program will increase step when gradients are smaller than the value of THETA_GRAD_THRESH, up to a limit of 0.5.
RECOMMENDATION:
       Try a smaller value in cases of poor convergence and very large orbital gradients. For example, a value of 01001 translates to 0.1

CC_TRANS_PROP
       Whether or not the transition dipole moment (in atomic units) and oscillator strength for the EOM-CCSD target states will be calculated. By default, the transition dipole moment and angular momentum matrix elements are calculated between the CCSD reference and the EOM-CCSD target states. In order to calculate transition dipole moment and angular momentum matrix elements 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 if transition properties between the CCSD reference and EOM-CCSD target states are requested) need to be solved for transition properties, approximately doubling the computational cost. The cost of the transition properties calculation itself is low.

CC_T_CONV
       Convergence criterion on the RMS difference between successive sets of coupled-cluster doubles amplitudes [${10}^{-n}$]
TYPE:
       INTEGER
DEFAULT:
       8 energies 10 gradients
OPTIONS:
       $n$ ${10}^{-n}$ convergence criterion.
RECOMMENDATION:
       Use default

CC_Z_CONV
       Convergence criterion on the RMS difference between successive doubles $Z$-vector amplitudes [${10}^{-n}$].
TYPE:
       INTEGER
DEFAULT:
       8 Energies 10 Gradients
OPTIONS:
       $n$ ${10}^{-n}$ convergence criterion.
RECOMMENDATION:
       Use Default

CDFTCI_PRINT
       Controls level of output from CDFT-CI procedure to Q-Chem output file.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Only print energies and coefficients of CDFT-CI final states 1 Level 0 plus CDFT-CI overlap, Hamiltonian, and population matrices 2 Level 1 plus eigenvectors and eigenvalues of the CDFT-CI population matrix 3 Level 2 plus promolecule orbital coefficients and energies
RECOMMENDATION:
       Level 3 is primarily for program debugging; levels 1 and 2 may be useful for analyzing the coupling elements

CDFTCI_RESTART
       To be used in conjunction with CDFTCI_STOP, this variable causes CDFT-CI to read already-converged states from disk and begin SCF convergence on later states. Note that the same $cdft section must be used for the stopped calculation and the restarted calculation.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       $n$ Start calculations on state $n+1$
RECOMMENDATION:
       Use this setting in conjunction with CDFTCI_STOP.

CDFTCI_SKIP_PROMOLECULES
       Skips promolecule calculations and allows fractional charge and spin constraints to be specified directly.
TYPE:
       BOOLEAN
DEFAULT:
       FALSE
OPTIONS:
       FALSE Standard CDFT-CI calculation is performed. TRUE Use the given charge/spin constraints directly, with no promolecule calculations.
RECOMMENDATION:
       Setting to TRUE can be useful for scanning over constraint values.

CDFTCI_STOP
       The CDFT-CI procedure involves performing independent SCF calculations on distinct constrained states. It sometimes occurs that the same convergence parameters are not successful for all of the states of interest, so that a CDFT-CI calculation might converge one of these diabatic states but not the next. This variable allows a user to stop a CDFT-CI calculation after a certain number of states have been converged, with the ability to restart later on the next state, with different convergence options.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       $n$ Stop after converging state $n$ (the first state is state $1$) $0$ Do not stop early
RECOMMENDATION:
       Use this setting if some diabatic states converge but others do not.

CDFTCI_SVD_THRESH
       By default, a symmetric orthogonalization is performed on the CDFT-CI matrix before diagonalization. If the CDFT-CI overlap matrix is nearly singular (i.e., some of the diabatic states are nearly degenerate), then this orthogonalization can lead to numerical instability. When computing ${𝐒}^{-1/2}$, 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
       Initiates a constrained DFT-configuration interaction calculation
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       TRUE Perform a CDFT-CI Calculation FALSE No CDFT-CI
RECOMMENDATION:
       Set to TRUE if a CDFT-CI calculation is desired.

CDFT_BECKE_POP
       Whether the calculation should print the Becke atomic charges at convergence
TYPE:
       LOGICAL
DEFAULT:
       TRUE
OPTIONS:
       TRUE Print Populations FALSE Do not print them
RECOMMENDATION:
       Use 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_CRASHONFAIL
       Whether the calculation should crash or not if the constraint iterations do not converge.
TYPE:
       LOGICAL
DEFAULT:
       TRUE
OPTIONS:
       TRUE Crash if constraint iterations do not converge. FALSE Do not crash.
RECOMMENDATION:
       Use the default.

CDFT_LAMBDA_MODE
       Allows CDFT potentials to be specified directly, instead of being determined as Lagrange multipliers.
TYPE:
       BOOLEAN
DEFAULT:
       FALSE
OPTIONS:
       FALSE Standard CDFT calculations are used. TRUE Instead of specifying target charge and spin constraints, use the values from the input deck as the value of the Becke weight potential
RECOMMENDATION:
       Should usually be set to FALSE. Setting to TRUE can be useful to scan over different strengths of charge or spin localization, as convergence properties are improved compared to regular CDFT(-CI) calculations.

CDFT_POP
       Sets the charge partitioning scheme for cDFT in SAPT/cDFT
TYPE:
       STRING
DEFAULT:
       FBH
OPTIONS:
       FBH Fragment-Based Hirshfeld partitioning BECKE Atomic Becke partitioning
RECOMMENDATION:
       None

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
       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.