OCC

Performs orbital-optimized MPn and CC computations and conventional MPn computations.

General

CACHELEVEL

Caching level for libdpd governing the storage of amplitudes, integrals, and intermediates in the CC procedure. A value of 0 retains no quantities in cache, while a level of 6 attempts to store all quantities in cache. For particularly large calculations, a value of 0 may help with certain types of memory problems. The default is 2, which means that all four-index quantities with up to two virtual-orbital indices (e.g., \(\langle ij | ab \rangle\) integrals) may be held in the cache.

  • Type: integer

  • Default: 2

CCL_ENERGY

Do compute CC Lambda energy? In order to this option to be valid one should use “TPDM_ABCD_TYPE = COMPUTE” option.

CC_MAXITER

Maximum number of iterations to determine the amplitudes

  • Type: integer

  • Default: 50

CEPA_OS_SCALE

Removed in 1.4. Will raise an error in 1.5.

  • Type: double

  • Default: 1.27

CEPA_SOS_SCALE

Removed in 1.4. Will raise an error in 1.5.

  • Type: double

  • Default: 1.3

CEPA_SS_SCALE

Removed in 1.4. Will raise an error in 1.5.

  • Type: double

  • Default: 1.13

CEPA_TYPE

CEPA type such as CEPA0, CEPA1 etc. currently we have only CEPA0.

  • Type: string

  • Possible Values: CEPA0

  • Default: CEPA0

CUTOFF

Cutoff value for numerical procedures

  • Type: integer

  • Default: 14

DIIS_MAX_VECS

Maximum number of error vectors stored for DIIS extrapolation

  • Type: integer

  • Default: 6

DIIS_MIN_VECS

Minimum number of error vectors stored for DIIS extrapolation

  • Type: integer

  • Default: 2

DO_DIIS

Do apply DIIS extrapolation?

DO_LEVEL_SHIFT

Removed in 1.4. Will raise an error in 1.5.

DO_SCS

Removed in 1.4. Will raise an error in 1.5. Pass the method name, like scs-mp2, to energy instead.

DO_SOS

Removed in 1.4. Will raise an error in 1.5. Pass the method name, like scs-mp2, to energy instead.

E3_SCALE

Scaling value for 3rd order energy correction (S. Grimme, Vol. 24, pp. 1529, J. Comput. Chem.)

  • Type: double

  • Default: 0.25

EA_POLES

Do compute OCC poles for electron affinities? Only valid for OMP2.

EKT_EA

Do compute virtual orbital energies based on extended Koopmans’ theorem?

EKT_IP

Do compute occupied orbital energies based on extended Koopmans’ theorem?

EP_EA_POLES

Do compute EP-OCC poles for electron affinities? Only valid for OMP2.

EP_IP_POLES

Do compute EP-OCC poles for ionization potentials? Only valid OMP2.

EP_MAXITER

Maximum number of electron propagator iterations.

  • Type: integer

  • Default: 30

E_CONVERGENCE

Convergence criterion for energy. See Table Post-SCF Convergence for default convergence criteria for different calculation types.

IP_POLES

Do compute OCC poles for ionization potentials? Only valid OMP2.

LEVEL_SHIFT

Removed in 1.4. Will raise an error in 1.5.

  • Type: double

  • Default: 0.02

MAX_MOGRAD_CONVERGENCE

Convergence criterion for maximum orbital gradient. If this keyword is not set by the user, OCC will estimate and use a value required to achieve the desired E_CONVERGENCE The listed default will be used for the default value of E_CONVERGENCE

MOGRAD_DAMPING

Damping factor for the orbital gradient (Rendell et al., JCP, vol. 87, pp. 5976, 1987)

  • Type: double

  • Default: 1.0

MO_MAXITER

Maximum number of iterations to determine the orbitals

  • Type: integer

  • Default: 50

MO_READ

Do read coefficient matrices from external files of a previous OMP2 or OMP3 computation?

MO_STEP_MAX

Maximum step size in orbital-optimization procedure

  • Type: double

  • Default: 0.5

MO_WRITE

Do write coefficient matrices to external files for direct reading MOs in a subsequent job?

MP2_OS_SCALE

Removed in 1.4. Will raise an error in 1.5.

  • Type: double

  • Default: 6.0

MP2_SOS_SCALE

Removed in 1.4. Will raise an error in 1.5.

  • Type: double

  • Default: 1.3

MP2_SOS_SCALE2

Removed in 1.4. Will raise an error in 1.5.

  • Type: double

  • Default: 1.2

MP2_SS_SCALE

Removed in 1.4. Will raise an error in 1.5.

  • Type: double

  • Default: 1.0

NAT_ORBS

Do compute natural orbitals?

OCC_ORBS_PRINT

Do print OCC orbital energies?

OEPROP

Do compute one electron properties?

OPT_METHOD

The optimization algorithm. Modified Steepest-Descent (MSD) takes a Newton-Raphson (NR) step with a crude approximation to diagonal elements of the MO Hessian. The ORB_RESP option obtains the orbital rotation parameters with a crude approximation to all elements of the MO Hessian. Additionally, for both methods a DIIS extrapolation will be performed with the DO_DIIS = TRUE option.

  • Type: string

  • Possible Values: MSD, ORB_RESP

  • Default: MSD

ORB_OPT

Do optimize the orbitals?

ORB_RESP_SOLVER

The algorithm will be used for solving the orbital-response equations. The LINEQ option create the MO Hessian and solve the simultaneous linear equations with method choosen by the LINEQ_SOLVER option. The PCG option does not create the MO Hessian explicitly, instead it solves the simultaneous equations iteratively with the preconditioned conjugate gradient method.

  • Type: string

  • Possible Values: PCG, LINEQ

  • Default: PCG

ORTH_TYPE

The algorithm for orthogonalization of MOs

  • Type: string

  • Possible Values: GS, MGS

  • Default: MGS

OS_SCALE

A custom scaling parameter for opposite-spin terms in OCC. The result goes to a CUSTOM SCS variable, exact name method-dependent.

  • Type: double

  • Default: 1

PCG_BETA_TYPE

Type of PCG beta parameter (Fletcher-Reeves or Polak-Ribiere).

  • Type: string

  • Possible Values: FLETCHER_REEVES, POLAK_RIBIERE

  • Default: FLETCHER_REEVES

PCG_CONVERGENCE

Convergence criterion for residual vector of preconditioned conjugate gradient method.

PCG_MAXITER

Maximum number of preconditioned conjugate gradient iterations.

  • Type: integer

  • Default: 30

RELAXED

Do consider orbital response contributions for PDMs and GFM?

REMP_A

mixing parameter for the REMP hybrid perturbation theory, A specifies the Moller-Plesset fraction

  • Type: double

  • Default: 0.15e0

RMS_MOGRAD_CONVERGENCE

Convergence criterion for RMS orbital gradient. If this keyword is not set by the user, OCC will estimate and use a value required to achieve the desired E_CONVERGENCE The listed default will be used for the default value of E_CONVERGENCE

R_CONVERGENCE

Convergence criterion for amplitudes (residuals).

SCS_TYPE

Type of the SCS method

  • Type: string

  • Possible Values: SCS, SCSN, SCSVDW, SCSMI

  • Default: SCS

SOS_TYPE

Type of the SOS method

  • Type: string

  • Possible Values: SOS, SOSPI

  • Default: SOS

SS_SCALE

A custom scaling parameter for same-spin terms in OCC. The result goes to a CUSTOM SCS variable, exact name method-dependent.

  • Type: double

  • Default: 1

SYMMETRIZE

Do symmetrize the GFM and OPDM in the EKT computations?

TPDM_ABCD_TYPE

How to take care of the TPDM VVVV-block. The COMPUTE option means it will be computed via an IC/OOC algorithm. The DIRECT option (default) means it will not be computed and stored, instead its contribution will be directly added to Generalized-Fock Matrix.

  • Type: string

  • Possible Values: DIRECT, COMPUTE

  • Default: DIRECT

WFN_TYPE

Type of the wavefunction.

  • Type: string

  • Possible Values: OMP2, OMP3, OCEPA, OMP2.5, REMP, OREMP

  • Default: OMP2

Expert

SPIN_SCALE_TYPE

Controls the spin scaling set to current energy. This is set by Psi internally.

  • Type: string

  • Possible Values: NONE, CUSTOM, SCS, SCSN, SCSVDW, SOS, SOSPI

  • Default: NONE