6.19.2 CAS-CI and CASSCF Job Control Options

CAS_METHOD
       Indicates whether orbital optimization is requested.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Not running a CAS calculation 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_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_SAVE_NAT_ORBS
       Save the CAS natural orbitals in place of the reference orbitals.
TYPE:
       BOOLEAN
DEFAULT:
       FALSE
OPTIONS:
       TRUE overwrite the reference orbitals with CAS natural orbitals FALSE do not save the CAS natural orbitals
RECOMMENDATION:
      

MAX_CASSCF_CYCLES
       Maximum number of orbital optimization cycles for CASSCF.
TYPE:
       INTEGER
DEFAULT:
       50
OPTIONS:
       $N$ set maximum number of optimization cycles to $N$
RECOMMENDATION:
      

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

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_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_SOLVER
       Specifies the solver to be used for the active space.
TYPE:
       INTEGER
DEFAULT:
       1
OPTIONS:
       1 CAS-CI/CASSCF 2 ASCI (see Section 6.21) 3 Truncated CI (CIS, CISD, CISDT, etc.)
RECOMMENDATION:
      

TRUNC_CI_LEVEL
       Specifies the order of truncated CI to be used in the active space.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Do not carry out truncated CI 1 CIS 2 CISD 3 CISDT 4 CISDTQ etc.
RECOMMENDATION: