$FORCE group                                                                    
(optional, relevant for RUNTYP=HESSIAN,OPTIMIZE,SADPOINT)                       
    This group controls the computation of the hessian                          
matrix (the energy second derivative tensor, also known                         
as the force constant matrix), and an optional harmonic                         
vibrational analysis.  This can be a very time consuming                        
calculation.  However, given the force constant matrix,                         
the vibrational analysis for an isotopically substituted                        
molecule is very cheap.  Related input is HESS= in                              
$STATPT, and the $MASS, $HESS, $GRAD, $DIPDR, $VIB inputs.                      
Calculation of the hessian automatically yields the dipole                      
derivative tensor, giving IR frequencies.  Raman                                
intensities are obtained by following with RUNTYP=RAMAN.                        
METHOD = chooses the computational method:                                      
       = ANALYTIC is a fully analytic calculation.  This                        
                  is implemented for SCFTYP=RHF, UHF, ROHF,                     
                  GVB (for NPAIR=0 or 1, only), and                             
                  MCSCF (for CISTEP=ALDET or ORMAS, only).                      
                  R-DFT and U-DFT are also analytic.                            
                  This is the default for these cases.                          
       = SEMINUM  does numerical differentiation of                             
                  analytically computed first derivatives.                      
                  This is the default for UHF, MCSCF using                      
                  other CISTEPs, all solvent models,                            
                  relativistic corrections, and most MP2 or                     
                  CI runs.                                                      
       = FULLNUM  numerically differentiates the energy                         
                  twice, which can be used by all other                         
                  cases.  It requires many energies (a                          
                  check run will tell how many) and so                          
                  it is mainly useful for systems with                          
                  only very few symmetry unique atoms.                          
The default for METHOD is to pick ANALYTIC over SEMINUM if                      
that is programmed, and SEMINUM otherwise.  FULLNUM will                        
never be chosen unless you specifically request it.                             
RDHESS = a flag to read the hessian from a $HESS input,                         
         rather than computing it.  This variable pertains                      
         only to RUNTYP=HESSIAN.  See also HESS= in the                         
         $STATPT input group.  (default is .FALSE.)                             
PURIFY = controls cleanup                                                       
         Given a $ZMAT, the hessian and dipole derivative                       
         tensor can be "purified" by transforming from                          
         Cartesians to internals and back to Cartesians.                        
         This effectively zeros the frequencies of the                          
         translation and rotation "modes", along with                           
         their IR intensities.  The purified quantities                         
         are punched out.  Purification does change the                         
         Hessian slightly, frequencies at a stationary                          
         point can change by a wave number or so.  The                          
         change is bigger at non-stationary points.                             
         (default=.FALSE. if $ZMAT is given)                                    
PRTIFC = prints the internal coordinate force constants.                        
         You MUST have provided $ZMAT input to use this.                        
  --- the next four apply to numeric differentiation ----                       
NVIB   =    The number of displacements in each Cartesian                       
            direction for force field computation.  This                        
            pertains only to METHOD=SEMINUM, as FULLNUM                         
            always uses double difference formulae.                             
       = 1  Move one VIBSIZ unit in each positive                               
            Cartesian direction.  This requires 3N+1                            
            evaluations of the wavefunction, energy, and                        
            gradient, where N is the number of SYMMETRY                         
            UNIQUE atoms given in $DATA.                                        
       = 2  Move one VIBSIZ unit in the positive direction                      
            and one VIBSIZ unit in the negative direction.                      
            This requires 6N+1 evaluations of the                               
            wavefunction and gradient, and gives a small                        
            improvement in accuracy.  In particular, the                        
            frequencies will change from NVIB=1 results by                      
            no more than 10-100 wavenumbers, and usually                        
            much less.  However, the normal modes will be                       
            more nearly symmetry adapted, and the residual                      
            rotational and translational "frequencies"                          
            will be much closer to zero. (default)                              
VIBSIZ =    Displacement size (in Bohrs). This pertains to                      
            Both SEMINUM and FULLNUM.  Default=0.01                             
       Let 0 mean the Vib0 geometry, and                                        
       D mean all the displaced geometries                                      
NPRT   = 1  Print orbitals at 0 and D                                           
       = 0  Print orbitals at 0 only (default)                                  
NPUN   = 2  Punch all orbitals at 0 and D                                       
       = 1  Punch all orbitals at 0 and occupied orbs at D                      
       = 0  Punch all orbitals at 0 only (default)                              
  ----- the rest control normal coordinate analysis ----                        
VIBANL = flag to activate vibrational analysis.                                 
         (the default is .TRUE. for RUNTYP=HESSIAN, and                         
         otherwise is .FALSE.)                                                  
SCLFAC = scale factor for vibrational frequencies, used                         
         in calculating the zero point vibrational energy.                      
         Some workers correct for the usual overestimate                        
         in SCF frequencies by a factor 0.89.  ZPE or other                     
         methods might employ other factors, see                                
            J.P.Merrick, D.Moran, L.Radom                                       
            J.Phys.Chem.A  111, 11683-11700 (2007).                             
         The output always prints unscaled frequencies, so                      
         this value is used only during the thermochemical                      
         analysis.  (Default is 1.0)                                            
TEMP   = an array of up to ten temperatures at which the                        
         thermochemistry should be printed out.  The                            
         default is a single temperature, 298.15 K.  To                         
         use absolute zero, input 0.001 degrees.                                
FREQ   = an array of vibrational frequencies.  If the                           
         frequencies are given here, the hessian matrix                         
         is not computed or read.  You enter any imaginary                      
         frequencies as negative numbers, omit the                              
         zero frequencies corresponding to translation                          
         and rotation, and enter all true vibrational                           
         frequencies.  Thermodynamic properties will be                         
         printed, nothing else is done by the run.                              
PRTSCN = flag to print contribution of each vibrational                         
         mode to the entropy.  (Default is .FALSE.)                             
DECOMP = activates internal coordinate analysis.                                
         Vibrational frequencies will be decomposed into                        
         "intrinsic frequencies", by the method of                              
         J.A.Boatz and M.S.Gordon, J.Phys.Chem., 93,                            
         1819-1826(1989).  If set .TRUE., the $ZMAT input                       
         may define more than 3N-6 (3N-5) coordinates.                          
PROJCT = controls the projection of the hessian matrix.                         
         The projection technique is described by                               
         W.H.Miller, N.C.Handy, J.E.Adams in J. Chem.                           
         Phys. 1980, 72, 99-112.  At stationary points,                         
         the projection simply eliminates rotational and                        
         translational contaminants.  At points with                            
         non-zero gradients, the projection also ensures                        
         that one of the vibrational modes will point                           
         along the gradient, so that there are a total of                       
         7 zero frequencies.  The other 3N-7 modes are                          
         constrained to be orthogonal to the gradient.                          
         Because the projection has such a large effect on                      
         the hessian, the hessian is punched both before                        
         and after projection.  For the same reason, the                        
         default is .FALSE. to skip the projection, which                       
         is mainly of interest in dynamical calculations.                       
There is a program ISOEFF for the calculation of kinetic                        
and equilibrium isotope effects from the group of Piotr                         
Paneth at the Technical University of Lodz.  This program                       
will accepts data computed by GAMESS (and other programs),                      
and can be requested from paneth@p.lodz.pl                                      

generated on 7/7/2017