$CIDRT group (required if CITYP=GUGA) This group describes the Configuration State Functions (CSFs) used by the MCSCF or CI calculation. The Distinct Row Table (DRT) is the means by which the Graphical Unitary Group Approach (GUGA) specifies configurations. The group is spelled $DRT for MCSCF runs, and $CIDRT for CI runs. The main difference in these is NMCC versus NFZC. There is no default for GROUP, and you must choose one of FORS, FOCI, SOCI, or IEXCIT. GROUP = the name of the point group to be used. This is usually the same as that in $DATA, except for RUNTYP=HESSIAN, when it must be C1. Choose from the following: C1, C2, CI, CS, C2V, C2H, D2, D2H, C4V, D4, D4H. If your $DATA's group is not listed, choose only C1 here. FORS = flag specifying the Full Optimized Reaction Space set of configuration should be generated. This is usually set true for MCSCF runs, but if it is not, see FORS in $MCSCF. (Default=.FALSE.) FOCI = flag specifying first order CI. In addition to the FORS configurations, all singly excited CSFs from the FORS reference are included. Default=.FALSE. SOCI = flag specifying second order CI. In addition to the FORS configurations, all singly and doubly excited configurations from the FORS reference are included. (Default=.FALSE.) IEXCIT= electron excitation level, for example 2 will lead to a singles and doubles CI. This variable is computed by the program if FORS, FOCI, or SOCI is chosen, otherwise it must be entered. INTACT= flag to select the interacting space option. See C.F.Bender, H.F.Schaefer J.Chem.Phys. 55, 4798-4803(1971). The CI will include only those CSFs which have non-vanishing spin couplings with the reference configuration. Note that when the Schaefer group uses this option for high spin ROHF references, they use Guest/Saunders orbital canonicalization. * * the next variables define the single reference * * The single configuration reference is defined by filling in the orbitals by each type, in the order shown. The default for each type is 0. Core orbitals, which are always doubly occupied: NMCC = number of MCSCF core MOs (in $DRT only). NFZC = number of CI frozen core MOs (in $CIDRT only). Internal orbitals, which are partially occupied: NDOC = number of doubly occupied MOs in the reference. NAOS = number of alpha occupied MOs in the reference, which are singlet coupled with a corresponding number of NBOS orbitals. NBOS = number of beta spin singly occupied MOs. NALP = number of alpha spin singly occupied MOs in the reference, which are coupled high spin. NVAL = number of empty MOs in the reference. External orbitals, occupied only in FOCI or SOCI: NEXT = number of external MOs. If given as -1, this will be set to all remaining orbitals (apart from any frozen virtual orbitals). NFZV = number of frozen virtual MOs, never occupied. * * the next two help with state symmetry * * STSYM= The symmetry of the electronic state. See $DET for possible values: use AP/APP in Cs, not primes. Default is the totally symmetric representation. note: This option overwrites whatever symmetry is implied by NALP/NAOS/NBOS. It is easier to pick STSYM than to allow its inference from the singly occupied orbitals, which is a relic of ancient input files. NOIRR= controls labelling of the CI state symmetries. = 1 no labelling (default) = 0 usual labelling. This can be very time consuming if the group is non-Abelian. =-1 fast labelling, in which all CSFs with small CI coefficients are ignored. This can produce weights quite different from one, due to ignoring small coefficients, but overall seems to work OK. Note that it is normal for the weights not to sum to 1 even for NOIRR=0 because for simplicity the weight determination is focused on the relative weights rather than absolute. However weight do not sum to one only for row-mixed MOs. = -2,-3... fast labelling and sets SYMTOL=10**NOIRR for runs other than TRANSITN. All irreps with weights greater than SYMTOL are considered. * * * the final choices are seldom used * * * MXNINT = Buffer size for sorted integrals. (default=20000) Adjust this upwards if the program tells you to, which may occur in cases with large numbers of external orbitals. MXNEME = Buffer size for energy matrix. (default=10000) NPRT = Configuration printout control switch. This can consume a HUMUNGUS amount of paper! 0 = no print (default) 1 = print electron occupancies, one per line. 2 = print determinants in each CSF. 3 = print determinants in each CSF (for Ms=S-1). ========================================================== ==========================================================

generated on 7/7/2017