PSIMRCC

Performs multireference coupled cluster computations. This theory should be used only by advanced users with a good working knowledge of multireference techniques.

General

ACTIVE

The number of active orbitals per irrep

• Type: array
• Default: No Default

CC_NUM_THREADS

Number of threads

• Type: integer
• Default: 1

CORR_ANSATZ

The ansatz to use for MRCC computations

• Type: string
• Possible Values: SR, MK, BW, APBW
• Default: MK

CORR_CCSD_T

The type of CCSD(T) computation to perform

• Type: string
• Possible Values: STANDARD, PITTNER
• Default: STANDARD

CORR_CHARGE

The molecular charge of the target state

• Type: integer
• Default: 0

CORR_MULTP

The multiplicity, , of the target state. Must be specified if different from the reference .

• Type: integer
• Default: 1

CORR_REFERENCE

Reference wavefunction type used in MRCC computations

• Type: string
• Possible Values: RHF, ROHF, TCSCF, MCSCF, GENERAL
• Default: GENERAL

CORR_WFN

The type of correlated wavefunction

• Type: string
• Possible Values: PT2, CCSD, MP2-CCSD, CCSD_T
• Default: CCSD

COUPLING

The order of coupling terms to include in MRCCSDT computations

• Type: string
• Possible Values: NONE, LINEAR, QUADRATIC, CUBIC
• Default: CUBIC

COUPLING_TERMS

Do include the terms that couple the reference determinants?

• Type: boolean
• Default: true

DAMPING_PERCENTAGE

The amount (percentage) of damping to apply to the amplitude updates. 0 will result in a full update, 100 will completely stall the update. A value around 20 (which corresponds to 20% of the amplitudes from the previous iteration being mixed into the current iteration) can help in cases where oscillatory convergence is observed.

• Type: double
• Default: 0.0

DIAGONALIZE_HEFF

Do diagonalize the effective Hamiltonian?

• Type: boolean
• Default: false

DIAGONAL_CCSD_T

Do include the diagonal corrections in (T) computations?

• Type: boolean
• Default: true

DIIS_MAX_VECS

Maximum number of error vectors stored for DIIS extrapolation

• Type: integer
• Default: 7

DIIS_START

The number of DIIS vectors needed before extrapolation is performed

• Type: integer
• Default: 2

E_CONVERGENCE

Convergence criterion for energy.

• Type: conv double
• Default: 1e-9

FAVG_CCSD_T

Do use the averaged Fock matrix over all references in (T) computations?

• Type: boolean
• Default: false

FOLLOW_ROOT

Which root of the effective hamiltonian is the target state?

• Type: integer
• Default: 1

FROZEN_DOCC

The number of frozen occupied orbitals per irrep

• Type: array
• Default: No Default

FROZEN_UOCC

The number of frozen virtual orbitals per irrep

• Type: array
• Default: No Default

HEFF4

Do include the fourth-order contributions to the effective Hamiltonian?

• Type: boolean
• Default: true

HEFF_PRINT

Do print the effective Hamiltonian?

• Type: boolean
• Default: false

LOCK_SINGLET

Do lock onto a singlet root?

• Type: boolean
• Default: false

MAXITER

Maximum number of iterations to determine the amplitudes

• Type: integer
• Default: 100

MP2_CCSD_METHOD

How to perform MP2_CCSD computations

• Type: string
• Possible Values: I, IA, II
• Default: II

MP2_GUESS

Do start from a MP2 guess?

• Type: boolean
• Default: true

NO_SINGLES

Do ?

• Type: boolean
• Default: false

OFFDIAGONAL_CCSD_T

Do include the off-diagonal corrections in (T) computations?

• Type: boolean
• Default: true

PT_ENERGY

The type of perturbation theory computation to perform

• Type: string
• Possible Values: SECOND_ORDER, SCS_SECOND_ORDER, PSEUDO_SECOND_ORDER, SCS_PSEUDO_SECOND_ORDER
• Default: SECOND_ORDER

RESTRICTED_DOCC

The number of doubly occupied orbitals per irrep

• Type: array
• Default: No Default

R_CONVERGENCE

Convergence criterion for amplitudes (residuals).

• Type: conv double
• Default: 1e-9

SMALL_CUTOFF

• Type: integer
• Default: 0

TIKHONOW_MAX

The cycle after which Tikhonow regularization is stopped. Set to zero to allow regularization in all iterations

• Type: integer
• Default: 5

TIKHONOW_OMEGA

The shift to apply to the denominators, {it c.f.} Taube and Bartlett, JCP, 130, 144112 (2009)

• Type: double
• Default: 0.0

TRIPLES_ALGORITHM

The type of algorithm to use for (T) computations

• Type: string
• Possible Values: SPIN_ADAPTED, RESTRICTED, UNRESTRICTED
• Default: RESTRICTED

TRIPLES_DIIS

Do use DIIS extrapolation to accelerate convergence for iterative triples excitations?

• Type: boolean
• Default: false

USE_SPIN_SYM

Do use symmetry to map equivalent determinants onto each other, for efficiency?

• Type: boolean
• Default: true

WFN_SYM

The symmetry of the target wavefunction, specified either by Schönflies symbol, or irrep number (in Cotton ordering)

• Type: string
• Possible Values: A, AG, AU, AP, APP, A1, A2, B, BG, BU, B1, B2, B3, B1G, B2G, B3G, B1U, B2U, B3U, 0, 1, 2, 3, 4, 5, 6, 7, 8
• Default: 1

ZERO_INTERNAL_AMPS

Do zero the internal amplitudes, i.e., those that map reference determinants onto each other?

• Type: boolean
• Default: true

Expert

PERTURB_CBS

Do compute the perturbative corrections for basis set incompleteness?

• Type: boolean
• Default: false

PERTURB_CBS_COUPLING

Do include the terms that couple different reference determinants in perturbative CBS correction computations?

• Type: boolean
• Default: true

TIKHONOW_TRIPLES

Do use Tikhonow regularization in (T) computations?

• Type: boolean
• Default: false

USE_SPIN_SYMMETRY

Whether to use spin symmetry to map equivalent configurations onto each other, for efficiency

• Type: boolean
• Default: true