$MCQDPT group  (relevant if SCFTYP=MCSCF and 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 for                       
    Analytic gradients are not available.  Spin-orbit                           
coupling may be treated as a perturbation, included at the                      
same time as the energy perturbation.  If spin-orbit                            
calculations are performed, the input groups for each                           
multiplicity are named $MCQD1, $MCQD2, ... rather than                          
$MCQDPT.  Parallel calculation is enabled.                                      
   When applied to only one state, the theory is known as                       
multi-reference Moller-Plesset (MRMP), but the term MCQDPT                      
is used when this theory is used in its multi-state form.                       
Please note that this perturbation theory is not the same                       
thing as the CASPT2 theory, and should -NEVER- be called                        
that.  A more complete discussion may be found in the                           
'Further Information' chapter.                                                  
   Most values will inherit sensible defaults for the state                     
symmetry and the orbital space counts from the $DET or $DRT                     
input defining the MCSCF: however for multi-state runs, the                     
user probably has to supply the desired state and weighting                     
   In case of diabatic state generation at the MCQDPT                           
level, the settings for state selection and weights will be                     
inherited from the $DIABAT input, to be the same as used                        
for the Diabatic MO generation.  Thus diabatization runs                        
will probably not give any input here, although they might                      
override NMOFZC/NMODOC defaults.                                                
       *** MCSCF reference wavefunction ***                                     
NEL    =   total number of electrons, including core.                           
           (default from $DATA and ICHARG in $CONTRL)                           
MULT   =   spin multiplicity (default from $CONTRL)                             
NMOACT =   Number of orbitals in FORS active space                              
           (default is the active space in $DET or $DRT)                        
NMOFZC =   number of frozen core orbitals, NOT correlated                       
           in the perturbation calculation.  (default is                        
           number of chemical cores)                                            
NMODOC =   number of orbitals which are doubly occupied in                      
           every MCSCF configuration, that is, not active                       
           orbitals, which are to be included in the                            
           perturbation calculation.  (The default is all                       
           valence orbitals between the chemical core and                       
           the active space)                                                    
NMOFZV =   number of frozen virtuals, NOT occupied during                       
           the perturbation calculation.  The default is                        
           to use all virtuals in the MP2.  (default=0)                         
If the input file does not provide a $DET or $DRT, the user                     
must give NMOFZC, NMODOC, and NMOACT correctly here.                            
STSYM = The symmetry of the target electronic state(s).                         
        See $DET for possible values: use AP/APP in Cs, not                     
        primes.  This must be given, and need not match the                     
        state symmetry used in optimizing the orbitals by                       
        $DET or $DRT, although it often does.                                   
        Default is the totally symmetric representation.                        
NOSYM  = 0 use CSF symmetry (see the STSYM keyword).                            
           off diagonal perturbations vanish if states are                      
           of different symmetry, so the most efficient                         
           computation is a separate run for every space                        
           symmetry. (default)                                                  
         1 turn off CSF state symmetry so that all states                       
           are treated at once.  STSYM is ignored.                              
           Presently this option does not seem to work!!                        
        -1 Symmetry purify the orbitals.  Since $GUESS is                       
           not read by MCQDPT runs, this option can be used                     
           as a substitute for its PURIFY.  After cleaning                      
           the orbitals, they are reorthogonalised within                       
           each irrep and within each group (core, double,                      
           active, virtual) separately.  Since this occurs                      
           without MCSCF optimization if you have chosen to                     
           use RDVECS in $MRMP, it is *your* responsibility                     
           to ensure that any purification of the orbitals                      
           is small enough that the CAS energies for the                        
           original CASSCF and the CAS-CI performed during                      
           the MCQDPT are the same!                                             
       *** perturbation specification ***                                       
KSTATE=    state is used (1) or not (0) in the MCQDPT2.                         
           Maximum of 20 elements, including zeros.                             
           For example, if you want the perturbation                            
           correction to the second and the fourth roots,                       
           See also WSTATE.                                                     
           (normal default=1,0,0,0,0,0,0,...)                                   
           (default for DIABAT=.TRUE. will be from $DIABAT)                     
XZERO   a flag to choose the 0-th order Hamiltonian used,                       
        when more than one state is included by KSTATE and                      
        WSTATE. XZERO has no impact on single state runs.                       
        .TRUE.  selects Granovsky's XMCQDPT equations for                       
        the zero-th order Hamiltonian, see                                      
          A.A.Granovsky, J.Chem.Phys. 134, 214113(2011).                        
        .FALSE. selects the original definition of the                          
        unperturbed Hamiltonian.  The default is .FALSE.                        
        *** Intruder State Removal ***                                          
EDSHFT =   energy denominator shifts.  (default=0.0,0.0)                        
           See also REFWGT.                                                     
Intruder State Avoidance (ISA) calculations can be made by                      
changing the energy denominators around poles (where the                        
denominator is zero).  Each denominator x is replaced by x                      
+ EDSHFT/x, so that far from the poles (when x is large)                        
the effect of such change is small.  EDSHFT is an array of                      
two values, the first is used in spin-free MCQDPT, and the                      
second is for spin-orbit MCQDPT.  Both values are used if                       
RUNTYP=TRNSTN, only the first is used otherwise.  A                             
suggested pair of values is 0.02,0.1, but experimentation                       
with your system is recommended.  Setting these values to                       
zero is ordinary MCQDPT, whereas infinite collapses to the                      
MCSCF reference.                                                                
Note that the energy denominators (which are ket-dependent                      
in MCQDPT) are changed in a different way for each ket-                         
vector, that is, for each row in MCQDPT Hamiltonian matrix.                     
In other words, the zeroth order energies are not                               
"universal", but state specific.  This is strictly speaking                     
an inconsistency in defining zeroth order energies that are                     
usually chosen "universally".                                                   
In order to maintain continuity when studying a PES, one                        
usually uses the same EDSHFT values for all points on PES.                      
In order to study the potential surface for any extended                        
range of geometries, it is recommended to use ISA, as it is                     
quite likely that one or more regions of the PES will be                        
unphysical due to intruder states.                                              
For an example of how intruder states can appear at some                        
points on the PES, see Figures 1,2,7 of                                         
    K.R.Glaesemann, M.S.Gordon, H.Nakano                                        
       Phys.Chem.Chem.Phys. 1, 967-975(1999)                                    
and also                                                                        
    H.A.Witek, D.G.Fedorov, K.Hirao, A.Viel, P.-O.Widmark                       
       J.Chem.Phys. 116, 8396-406(2002)                                         
For a discussion of intruder state removal from MCQDPT, see                     
    H.A.Witek, Y.-K.Choe, J.P.Finley, K.Hirao                                   
       J.Comput.Chem. 23, 957-965(2002)                                         
REFWGT =   a flag to request decomposition of the second                        
           order energy into internal, semi-internal, and                       
           external contributions, and to obtain the weight                     
           of the MCSCF reference in the 1st order wave                         
           function.  This option significantly increases                       
           the run time!  When you run in parallel, only                        
           the transformation steps will speed up, as the                       
           PT part of the reference weight calculation has                      
           not been adapted for speedups (default=.FALSE.)                      
           The EDSHFT option does not apply if REFWGT is                        
           used.  One purpose of using REFWGT is to try to                      
           understand the nature of the intruder states.                        
       *** Canonical Fock orbitals ***                                          
IFORB  = 0 skip canonicalization                                                
           (default when DIABAT=.TRUE.).                                        
       = 1 determine the canonical Fock orbitals.                               
           (the usual default)                                                  
       = 3 canonicalise the Fock orbitals averaged over                         
           all $MCQDx input groups.                                             
IFORB=3 option pertains only to RUNTYP=TRANSITN.  It is                         
primarily meant to include spin-orbit coupling perturbation                     
into the energy perturbation, but could also be used in                         
conjunction with OPERAT=DM to calculate only the second                         
order energy perturbation.  IFORB=3 means that WSTATE is                        
used as follows:  In each $MCQDx group, the WSTATE weights                      
are divided by the total number of states (sum(i)                               
IROOTS(i)), so the sum over all WSTATE values in all $MCQDx                     
groups is normalized to sum to 1.  Thus there is no                             
normalization to 1 within each $MCQDx group.                                    
This option might be used to speed up an atomic MCQDPT,                         
e.g. if computing the 3-P ground state of carbon, one would                     
want to average over all three spatial components of the P                      
term, to be sure of spatial degeneracy, but then run the                        
perturbation using symmetry, separately on the B1g+B2g+B3g                      
subspecies (within D2h) of a P term. It is very important                       
to give weights appropriate for the symmetry, the input                         
requires care.                                                                  
WSTATE =   weight of each CAS-CI state in computing the                         
           closed shell Fock matrix.  You must enter 0.0                        
           whenever the same element in KSTATE is 0.                            
           In most cases setting the WSTATEs for states                         
           to be included in the MCQDPT to equal weights                        
           is the best, and this is the default.                                
           Runs with DIABAT=.TRUE. default to the same                          
           weights used during the DMO generation step.                         
       *** Miscellaneous options ***                                            
ISELCT     is an option to select only the important CSFs                       
           for inclusion into the CAS-CI reference states.                      
           Set to 1 to select, or 0 to avoid selection of                       
           CSFs (default = 0)                                                   
           All CSFs in a preliminary complete active space                      
           CI whose CI coefficients exceed the square root                      
           of THRWGT are kept in a smaller CI to determine                      
           the zero-th order states.  Note that the CSFs                        
           with smaller coefficients, while excluded from                       
           the reference states, are still used during the                      
           perturbation calculation, so most of their                           
           energy contribution is still retained.  This can                     
           save appreciable computer time in cases with                         
           large active spaces.                                                 
THRWGT =   weight threshold for retaining CSFs in selected                      
           configuration runs.  In quantum mechanics, the                       
           weight of a CSF is the square of its CI                              
           coefficient.  (default=1d-6)                                         
THRGEN =   threshold for one-, two-, and three-body                             
           density matrix elements in the perturbation                          
           calculation.  The default gives about 5 decimal                      
           place accuracy in energies.  Increase to 1.0D-12                     
           if you wish to obtain higher accuracy, for                           
           example, in numerical gradients (default=1D-8).                      
           Tightening THRGRN and perhaps CI diagonalization                     
           should allow 7-8 decimal place agreement with                        
           the determinant code.                                                
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)                         
MDI    =   dimension of small Hamiltonian diagonalized to                       
           prepare initial guess CI states. (default=50)                        
MXBASE =   maximum number of expansion vectors in the                           
           Davidson diagonalization subspace (e.g. MXXPAN).                     
NSOLUT =   number of states to be solved for in the                             
           Davidson's method, this might need to exceed                         
           the number of states in the perturbation                             
           treatment in order to "capture" the correct                          
NSTOP  =   maximum number of iterations to permit in                            
           the Davidson's diagonalization.                                      
LPOUT  =   print option, 0 gives normal printout, while                         
           <0 gives debug print (e.g. -1, -5, -10, -100)                        
           In particular, LPOUT=-1 gives more detailed                          
           timing information.  (default=0)                                     
The next three parameters refer to parallel execution:                          
DOORD0 =   a flag to select reordering of AO integrals                          
           which speeds the integral transformations.                           
           This reduces disk writes, but increases disk                         
           reads, so you can try turning it off if your                         
           machine has slow writes.  (default=.TRUE.)                           
PARAIO =   access 2e- integral file on every node, at                           
           the same time.  This affects only runs with                          
           DOORD0 true, and it may be useful to turn                            
           this off in the case of SMP nodes sharing                            
           a common disk drive.  (default=.TRUE.)                               
DELSCR =   a flag to delete file 56 containing half-                            
           transformed integrals after it has been                              
           used.  This reduces total disk requirements                          
           if this file is big.  (default=.FALSE.)                              
Note that parallel execution will be more effective if you                      
use distributed memory, MEMDDI in $SYSTEM.  Using                               
AOINTS=DIST in $TRANS is likely to be helpful in situations                     
with relatively poor I/O rates compared to communication,                       
e.g. SMP enclosures forced to share a single scratch disk                       
system.  See PROG.DOC for more information on parallel                          
Finally, there are additional very specialized options,                         
described in the source code routine MQREAD: IROT, LENGTH,                      

generated on 7/7/2017