7.12.13 Job Control Options forlibrassf‣ 7.12 Restricted Active Space Spin-Flip (RAS-SF) and Configuration Interaction (RAS-CI) ‣ Chapter 7 Open-Shell and Excited-State Methods ‣ Q-Chem 5.4 User’s Manual

The librassf module can be enabled by setting EXCHANGE = HF, CORRELATION = RASCI2, and LIBRASSF = 1 in the $rem variable section. One should also indicate the number of roots by setting RAS_N_ROOTS appropriately. Although the module is called through RASCI2, most job control options are more similar to those found in RASCI1, with the exception of RAS_N_ROOTS.

The number of spin-flips and IP/EA are determined by the $rem variables RASSF_DELTA_ALPHA (the number of alpha electrons removed) and RASSF_DELTA_BETA (the number of beta electrons added). Hole and particle excitations can be added by setting the RAS_DO_HOLE and RAS_DO_PART keywords. Additionally, text files containing eigenvalues and eigenvectors can be printed via the RASSF_WRITE_EVALS and RASSF_WRITE_EVECS keywords.

RAS_N_ROOTS

RAS_N_ROOTS
       Sets the number of RAS-CI roots to be computed.
TYPE:
       INTEGER
DEFAULT:
       None
OPTIONS:
       $n$ $n>0$ Compute $n$ RAS-CI states
RECOMMENDATION:
       None.

RASSF_DELTA_ALPHA

RASSF_DELTA_ALPHA
       Sets the number of alpha electrons to remove relative to the reference.
TYPE:
       INTEGER
DEFAULT:
       None
OPTIONS:
       $0$ Remove no alpha electrons (use for EA) $1$ Remove one alpha electron (use for 1SF, IP) $2$ Remove two alpha electrons (use for 2SF, 1SF-IP)
RECOMMENDATION:
       None.

RASSF_DELTA_BETA

RASSF_DELTA_BETA
       Sets the number of beta electrons to add relative to the reference.
TYPE:
       INTEGER
DEFAULT:
       None
OPTIONS:
       $0$ Add no beta electrons (use for IP) $1$ Add one beta electron (use for 1SF, EA) $2$ Add two beta electrons (use for 2SF, 1SF-EA)
RECOMMENDATION:
       None.

RAS_DO_HOLE

RAS_DO_HOLE
       Enables hole excitations.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       $0$ No hole excitations (use for CAS or RAS(p)) $1$ Single hole excitations (use for RAS(h) or RAS(h,p))
RECOMMENDATION:
       None.

RAS_DO_PART

RAS_DO_PART
       Enables particle excitations.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       $0$ No particle excitations (use for CAS or RAS(h)) $1$ Single particle excitations (use for RAS(p) or RAS(h,p))
RECOMMENDATION:
       None.

N_FROZEN_CORE

N_FROZEN_CORE
       Number of frozen core orbitals.
TYPE:
       SIZE_T
DEFAULT:
       0
OPTIONS:
       $n$ $n\geq 0$ Number of frozen core orbitals.
RECOMMENDATION:
       None.

N_FROZEN_VIRTUAL

N_FROZEN_VIRTUAL
       Number of frozen virtual orbitals.
TYPE:
       SIZE_T
DEFAULT:
       0
OPTIONS:
       $n$ $n\geq 0$ Number of frozen virtual orbitals.
RECOMMENDATION:
       None.

RASSF_GUESS

RASSF_GUESS
       Determines which initial set of guess vectors to use for Davidson.
TYPE:
       INTEGER
DEFAULT:
       $2$
OPTIONS:
       $0$ Random orthonormal guess (default for CAS) $1$ Identity guess $2$ CAS guess (default for RAS)
RECOMMENDATION:
       Starting from a CAS guess is recommended for larger molecules. If Davidson encounters issues with linearly dependent eigenvectors, consider using identity. The random orthonormal guess requires building a large $N x N$ matrix and is therefore only recommended for calculations with fewer determinants.

RASSF_WRITE_EVALS

RASSF_WRITE_EVALS
       Determines whether to write eigenvalues to an output file.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       $0$ Do not write eigenvalues to an output file $1$ Write eigenvalues to an output file
RECOMMENDATION:
       None.

RASSF_WRITE_EVECS

RASSF_WRITE_EVECS
       Determines whether to write eigenvectors to an output file.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       $0$ Do not write eigenvectors to an output file $1$ Write eigenvectors to an output file
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_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.

RASSF_DO_BLOCH

RASSF_DO_BLOCH
       Determines whether to do effective Hamiltonian analysis.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       $0$ Skip analysis $1$ Do effective Hamiltonian analysis
RECOMMENDATION:
       None.

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7.12.13 Job Control Options for librassf