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$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).
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generated on 7/7/2017