$MCQDPT

$MCQDPT group (relevant to SCFTYP=MCSCF if MPLEVL=2)

Controls 2nd order MCQDPT (multiconfiguration quasi- degenerate perturbation theory) runs, if requested by MPLEVL=2 in $CONTRL. MCQDPT2 is implemented only for FORS (aka CASSCF) wavefunctions. The MCQDPT method is a multistate, as well as multireference perturbation theory. The implementation is a separate program, interfaced to GAMESS, with its own procedures for determination of the canonical MOs, CSF generation, integral transformation, CI in the reference CAS, etc. Therefore some of the input in this group repeats data given elsewhere, particularly the $DRT. A more complete discussion may be found in the 'Further Information' chapter. Analytic gradients are not available.

*** MO input and flow control ***

INORB

= 0 optimize the MCSCF wavefunction in this run.

= 1 read the converged orbitals from a $VEC group, and skip immediately to the MCQDPT computation. (default=0)

NEL

= total number of electrons, including core. (default from $DATA and ICHARG in $CONTRL)

MULT

= spin multiplicity (default from $CONTRL)

NMOFZC

= number of frozen core orbitals, NOT correlated in the perturbation calculation. (default=0)

NMODOC

= number of doubly occupied orbitals, correlated in the perturbation calculation. (default=0)

NMOACT

= number of active orbitals. (default=0)

NMOFZV

= number of frozen virtuals, NOT correlated in the perturbation calculation. (default=0)

ISTSYM

= the state symmetry of the target state(s). This is given as an integer, note that only Abelian groups are supported in $DATA:

            ISTSYM= 1   2   3   4   5   6   7   8
               C1   A
               Ci   Ag  Au
               Cs   A'  A''
               C2   A   B 
               C2v  A1  A2  B1  B2
               C2h  Ag  Bg  Au  Bu
               D2   A   B1  B2  B3
               D2h  Ag  B1g B2g B3g Au  B1u B2u B3u

The default is 1, the totally symmetric state.

*** perturbation specification ***

NSTATE

= number of target states, which is the dimension of the effective Hamiltonian. (default=1)

NSTCI

= number of states to be obtained in CAS-CI, which should equal or exceed NSTATE. (default=1, the maximum is 20)

KSTATE

= state is used (1) or not (0) in the MCQDPT2. (default=1,1,1,...)
For example, if you want the perturbation correction to the second and the fourth roots, NSTATE=2 NSTCI=4 KSTATE(1)=0,1,0,1

IFORB

= 1 determine the canonical Fock orbitals

= 0 omit this step. (default=1)

AVECOE

= weight of each CAS-CI state in computing the closed shell Fock matrix. (default is AVECOE(1)=1.0,1.0,1.0,...)

*** Miscellaneous options ***

THRGEN

= threshold for one-, two-, and three-body density matrix elements in the perturbation calculation. If you want to obtain energies, for instance, to 6 figures after point, choose THRGEN=1.0D-08 or 1.0D-09. (default=1.0D-08)

THRENE

= threshold for the energy convergence in the Davidson's method CAS-CI. (default=-1.0D+00)

THRCON

= threshold for the vector convergence in the Davidson's method CAS-CI. (default=1.0D-06)

LPOUT

= print option, 0 gives normal printout, while <0 gives debug print (e.g. -1,-5,-10,-100)

(default=0)

Finally, there are additional very specialized input options, described in the source code routine MQREAD:

IROT, ISELCT, LENGTH, MAXCSF, MAXERI, MAXROW, MDI, MXBASE, MXTRFR, NSOLUT, NSTOP, GENZRO, THRERI, THRWGT, MAINCS.