7.12 Restricted Active Space Spin-Flip (RAS-SF) and Configuration Interaction (RAS-CI)

7.12.8 Job Control Options for LibRASSF

LibRASSF 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 DO_HOLE and DO_PARTICLE keywords. Additionally, text files containing eigenvalues and eigenvectors can be printed via the RASSF_WRITE_EVALS and RASSF_WRITE_EVECS keywords.

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
       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
       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
       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
       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
       Number of frozen core orbitals.
TYPE:
       SIZE_T
DEFAULT:
       0
OPTIONS:
       n n≥0 Number of frozen core orbitals.
RECOMMENDATION:
       None.

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

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
       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.