$SCF group       relevant if SCFTYP = RHF, UHF, or ROHF,                        
                   required if SCFTYP = GVB)                                    
    This group of parameters provides additional control                        
over the RHF, UHF, ROHF, or GVB SCF steps.  It must be                          
given to define GVB open shell or perfect pairing                               
wavefunctions.  See $MCSCF for multireference inputs.                           
DIRSCF = a flag to activate a direct SCF calculation,                           
         which is implemented for all the Hartree-Fock                          
         type wavefunctions:  RHF, ROHF, UHF, and GVB.                          
         This keyword also selects direct MP2 computation.                      
         The default of .FALSE. stores integrals on disk                        
         storage for a conventional SCF calculation.                            
FDIFF  = a flag to compute only the change in the Fock                          
         matrices since the previous iteration, rather                          
         than recomputing all two electron contributions.                       
         This saves much CPU time in the later iterations.                      
         This pertains only to direct SCF, and has a                            
         default of .TRUE.  This option is implemented                          
         only for the RHF, ROHF, UHF cases.                                     
         Cases with many diffuse functions in the basis                         
         set, or large molecules, may sometimes be "mushy"                      
         at the end, rather than converging.  Increasing                        
         ICUT in $CONTRL by one may help this, or consider                      
         turning this parameter off.                                            
---- The next flags affect convergence rates.                                   
DIIS   = selects Pulay's DIIS interpolation.                                    
SOSCF  = selects second order SCF orbital optimization.                         
  Only one of DIIS or SOSCF may be .TRUE. in any run.                           
  Which is chosen by default depends on the run:                                
      for RHF, GVB, UHF, or ROHF (if Abelian): SOSCF.TRUE.                      
      for any DFT, or for non-Abelian groups:  DIIS=.TRUE.                      
NOCONV = .TRUE. means neither SOSCF nor DIIS will be used,                      
         specify NOCONV=.TRUE. DIIS=.FALSE. SOSCF=.FALSE.                       
         in the rare case you don't wish to use either one.                     
         NOCONV's default is .FALSE., meaning the program                       
         will obey your choice of DIIS/SOSCF, or else pick                      
         its default for them.                                                  
     Once either DIIS or SOSCF are initiated, the following                     
less important accelerators are placed in abeyance:                             
EXTRAP = selects Pople extrapolation of the Fock matrix.                        
DAMP   = selects Davidson damping of the Fock matrix.                           
SHIFT  = selects level shifting of the Fock matrix.                             
RSTRCT = selects restriction of orbital interchanges.                           
DEM    = selects direct energy minimization, which is                           
         implemented only for RHF.  (default=.FALSE.)                           
defaults for     EXTRAP  DAMP  SHIFT RSTRCT  DIIS  SOSCF                        
ab initio:         T      F      F      F     F/T   T/F                         
semiempirical:     T      F      F      F      F     F                          
     The above parameters are implemented for all SCF                           
wavefunction types, except that DIIS will work for GVB only                     
for those cases with NPAIR=0 or NPAIR=1.                                        
CUHF   = flag requesting Constrained UHF, which causes                          
         the occupied beta orbitals of a UHF run to lie                         
         entirely within the occupied alpha orbital space.                      
         This produces results identical to high spin                           
         ROHF!  Obviously, this keyword pertains only                           
         when using SCFTYP=UHF.  The default is .FALSE.,                        
         meaning a spin-contaminated ordinary UHF solution                      
         is sought.  Applicable to UHF or UDFT energy and                       
         gradients, or to UMP2 energy calculations.                             
---- These parameters fine tune the various convergers.                         
CONV   = SCF density convergence criteria.                                      
         Convergence is reached when the density change                         
         between two consecutive SCF cycles is less than                        
         this in absolute value.  One more cycle will be                        
         executed after reaching convergence.   Less                            
         accuracy in CONV gives questionable gradients.                         
         The default is 1.0d-05, except runs involving                          
         CI, MP2, CC, or TDDFT use 1.0d-06 to obtain more                       
         crisply converged virtual orbitals.                                    
SOGTOL = second order gradient tolerance.  SOSCF will be                        
         initiated when the orbital gradient falls below                        
         this threshold.  (default=0.25 au)                                     
ETHRSH = energy error threshold for initiating DIIS.  The                       
         DIIS error is the largest element of e=FDS-SDF.                        
         Increasing ETHRSH forces DIIS on sooner.                               
         (default = 0.5 Hartree)                                                
MAXDII = Maximum size of the DIIS linear equations, so                          
         that at most MAXDII-1 Fock matrices are used                           
         in the interpolation.  (default=10)                                    
SWDIIS = density matrix convergence at which to switch                          
         from DIIS to SOSCF.  A value of zero means to                          
         keep using DIIS at all geometries, which is the                        
         default.  However, it may be useful to have                            
         DIIS work only at the first geometry, in the                           
         initial iterations, for example transition                             
         metal ECP runs which has a less good Huckel                            
         guess, and then use SOSCF for the final SCF                            
         iterations at the first geometry, and ever                             
         afterwards.  A suggested usage might be                                
         DIIS=.TRUE. ETHRSH=2.0 SWDIIS=0.005.                                   
         This option is not programmed for GVB.                                 
LOCOPT = When set to .TRUE., SCF options are locked                             
         and do not change during the following:                                
         SOSCF and DIIS switch (SWDIIS), DFT grid switch,                       
         RHF -> DFT switch (SWOFF). If .FALSE., any                             
         of these switches resets some SCF options, such                        
         as SHIFT or DAMP.  (Default: .FALSE.)                                  
RESET  = In UHF, reset SOSCF or DIIS if energy rises                            
         (Default: .TRUE. for UHF, .FALSE. otherwise).                          
DEMCUT = Direct energy minimization will not be done                            
         once the density matrix change falls below                             
         this threshold.  (Default=0.5)                                         
DMPCUT = Damping factor lower bound cutoff.  The damping                        
         damping factor will not be allowed to drop                             
         below this value. (default=0.0)                                        
note: The damping factor need not be zero to achieve valid                      
convergence (see Hsu, Davidson, and Pitzer, J.Chem.Phys.,                       
65, 609 (1976), see the section on convergence control),                        
but it should not be astronomical either.                                       
        * * * * * * * * * * * * * * * * * * * * *                               
        For more info on the convergence methods,                               
        see the 'Further Information' section.                                  
        * * * * * * * * * * * * * * * * * * * * *                               
          ---- orbital modification options ----                                
    The four options UHFNOS, VVOS, MVOQ, and ACAVO are                          
mutually exclusive.  The latter 3 require RUNTYP=ENERGY,                        
and should not be used with any correlation treatment.                          
UHFNOS = flag controlling generation of the natural                             
         orbitals of a UHF function. (default=.FALSE.)                          
VVOS   = flag controlling generation of Valence Virtual                         
         Orbitals.  See J.Chem.Phys. 120, 2629-2637(2004).                      
         The default is .FALSE.                                                 
VVOs are a quantitative realization of the concept of the                       
"lowest unoccupied molecular orbital".  The implementation                      
allows any elements H-Xe, for RHF, ROHF, and GVB                                
wavefunctions, as well as DFT runs (see also VVOS in                            
$MCSCF).  Core potentials may not be used.  VVOS should be                      
much better MCSCF starting orbitals than either MVOQ or                         
ACAVO type virtuals.                                                            
MVOQ   = 0  Skip MVO generation (default)                                       
       = n  Form modified virtual orbitals, using a cation                      
            with n electrons removed.   Implemented for                         
            RHF, ROHF, and GVB.   If necessary to reach a                       
            closed shell cation, the program might remove                       
            n+1 electrons.  Typically, n will be about 6.                       
       = -1 The cation used will have each valence orbital                      
            half filled, to produce MVOs with valence-like                      
            character in all regions of the molecule.                           
            Implemented for RHF and ROHF only.                                  
ACAVO  =    Flag to request Approximate Correlation-Adapted                     
            Virtual Orbitals.  Implemented for RHF, ROHF,                       
            and GVB (w/o direct SCF).  Default is .FALSE.                       
PACAVO =    Parameters used to define the ACAVO generating                      
            operator, which is defined as                                       
          a*T + b*Vne + c*Jcore + d*Jval + e*Kcore + f*Kval                     
The default, PACAVO(1)=0,0,0,0,0,-1, maximizes the exchange                     
interaction with valence MOs (see for example J.L.Whitten,                      
J.Chem.Phys. 56, 5458-5466(1972).                                               
The K-orbitals of D.Feller, E.R.Davidson J.Chem.Phys. 74,                       
3977-3979(1981) are 0.06*F-K(valence), which is                                 
PACAVO(1)= 0.06,0.06,0.12,0.12,-0.06,-1.06.                                     
Of course, canonical virtuals are PACAVO(1)=1,1,2,2,-1,-1.                      
                       * * *                                                    
UHFCHK  = a flag to perform a RHF --> UHF wavefunction                          
          stability test (relaxation of RHF orbitals to                         
          unequal alpha and beta orbitals).  This option is                     
          implemented only for RHF, and involves testing                        
          only pairs of orbitals at a single time:                              
          this is not foolproof!   default is .FALSE.                           
NHOMO   = if UHFCHK is selected, the number of orbitals at                      
          The top of the occupied orbital space to be                           
          checked for instabilities.                                            
          Default= -1, meaning check HOMO and HOMO-1.                           
NLUMO   = if UHFCHK is selected, the number of orbitals                         
          at the bottom of the virtual space checked.                           
          Basis sets with diffuse functions should check                        
          many more orbitals, to get past the diffuse MOs.                      
          Default=2, meaning check LUMO, LUMO+1, LUMO+2.                        
                       * * *                                                    
MOM    = flag enabling the Molecular Overlap Method (MOM).                      
         Currently works only with SCFTYP=UHF.                                  
         MOM computes excitations by selecting orbitals at                      
         each iteration to resemble earlier iterations.                         
         See J.Phys.Chem. A 112, 13164-13171(2008).                             
note: MOM typically requires an initial MOREAD set of                           
ground-state MO's, reordered by NORDER=1 in conjunction                         
with the IORDER/JORDER arrays.                                                  
The MOM flag is an algorithm very similar to that enabled                       
by the RSTRCT flag.  Note: RSTRCT works with all SCF types.                     
KPROJ     determines the flavor of the MOM projections p_j                      
          obtained from the overlap matrix O(i,j).                              
          KPROJ pertains only if the MOM flag is enabled.                       
        = 0 p_j = |sum_i O(i,j)|                                                
                  as given in the original MOM article                          
        = 1 p_j = sum_i O(i,j)  (default)                                       
        = 2 p_j = sum_i O(i,j)*O(i,j),                                          
                  as implemented in Q-Chem                                      
            ----- GVB wavefunction input -----                                  
    The next parameters define the GVB wavefunction.  See                       
also MULT in the $CONTRL input.  The GVB wavefunction                           
assumes orbitals are in the order core, open, pairs.                            
NCO    =   The number of closed shell orbitals.  The                            
           default almost certainly should be changed!                          
NSETO  =   The number of sets of open shells in the                             
           function.  Maximum of 10. (default=0)                                
NO     =   An array giving the degeneracy of each open                          
           shell set.  Give NSETO values.                                       
NPAIR  =   The number of geminal pairs in the -GVB-                             
           function.  Maximum of 12.  The default                               
           corresponds to open shell SCF (default=0).                           
CICOEF =   An array of ordered pairs of CI coefficients                         
           for the -GVB- pairs.                                                 
           (default = 0.90,-0.20,0.90,-0.20,...)                                
For example, a two pair case for water, say, might be                           
CICOEF(1)=0.95,-0.05,0.95,-0.05.  If not normalized, as in                      
the default, CICOEF will be.  This parameter is useful in                       
restarting a GVB run, with the current CI coefficients.                         
COUPLE =   A switch controlling the input of F, ALPHA,                          
           and BETA. (Default=.FALSE.)                                          
Input for F, ALPHA, BETA will be ignored unless you select                      
this variable as .TRUE.                                                         
F      =   An vector of fractional shell occupations.                           
ALPHA  =   An array of A coupling coefficients, given in                        
           lower triangular order.                                              
BETA   =   An array of B coupling coefficients, given in                        
           lower triangular order.                                              
    Note:  The default for F, ALPHA, and BETA depends on                        
the state chosen.  Defaults for the most commonly occurring                     
cases are internally stored.  See "Further Information" for                     
other cases, including degenerate open shells.                                  
    Note: ALPHA and BETA can be given for -ROHF- orbital                        
canonicalization control, see "Further Information".                            
        ----- miscellaneous options -----                                       
NPUNCH =     option for output to the PUNCH file                                
       =  0  do not punch out the final orbitals                                
       =  1  punch out the occupied orbitals                                    
       =  2  punch out occupied and virtual orbitals                            
             The default is NPUNCH = 2.                                         
NPREO  = energy and orbital printing options, applied                           
         after other output options, for example NPRINT=-5                      
         for no orbital output overrules NPREO.  NPREO                          
         affects only printing, see NPUNCH just above.                          
         Default: 1,9999,2,1 (meaning print all orbitals,                       
         but no separate list of orbital energies).                             
         Orbitals from NPREO(1) to NPREO(2) and orbital                         
         energies from NPREO(3) to NPREO(4) are printed.                        
         Positive values are explicit orbitals, while                           
         negative numbers are relative to the HOMO.  Here,                      
         HOMO means NE/2, ie RHF-like counting, no matter                       
         what the SCFTYP actually is:                                           
             NPREO(1)=25,35   prints orbitals 25 to 35                          
             NPREO(1)=-3,-4   prints 8 orbitals: from 3                         
                              below the HOMO, the HOMO,                         
                              to 4 above the HOMO.                              
         NPREO(3) to NPREO(4) define separate print-out of                      
         the orbital energies, by default this is skipped,                      
         since the starting value is higher than the end.                       
         To print only HOMO and "LUMO" LCAO coefficients,                       
         and all orbital energies, enter:                                       
        ----- options for virial scaling -----                                  
VTSCAL =   A flag to request that the virial theorem be                         
           satisfied.  An analysis of the total energy                          
           as an exact sum of orbital kinetic energies                          
           is printed.  The default is .FALSE.                                  
This option is implemented for RHF, UHF, and ROHF, for                          
RUNTYP=ENERGY, OPTIMIZE, or SADPOINT.  Related input is:                        
SCALF  =   initial exponent scale factor when VTSCAL is                         
           in use, useful when restarting.  The default                         
           is 1.0.                                                              
MAXVT  =   maximum number of iterations (at a single                            
           geometry) to satisfy the energy virial theorem.                      
           The default is 20.                                                   
VTCONV =   convergence criterion for the VT, which is                           
           satisfied when 2 +  + R x dE/dR is less                        
           than VTCONV.  The default is 1.0D-6 Hartree.                         
For more information on this option, which is most useful                       
during a geometry search, see M.Lehd and F.Jensen,                              
J.Comput.Chem. 12, 1089-1096(1991).                                             
            * * * * * * * * * * * * * * * * * * *                               
            For more discussion of GVB/ROHF input                               
            see the 'further information' section                               
            * * * * * * * * * * * * * * * * * * *                               

generated on 7/7/2017