$HESS group                                                                     
            (relevant for RUNTYP=HESSIAN if RDHESS=.TRUE.)                      
         (relevant for RUNTYP=IRC if FREQ,CMODE not given)                      
      (relevant for RUNTYP=OPTIMIZE,SADPOINT if HESS=READ)                      
    Formatted force constant matrix (FCM), i.e. hessian                         
matrix.  This data is punched out by a RUNTYP=HESSIAN job,                      
in the correct format for subsequent runs.  The first card                      
in the group must be a title card.                                              
    $HESS information is always punched in Cartesians.  It                      
will be transformed into internal coordinate space if a                         
geometry search uses internals.  It will be mass weighted                       
(according to $MASS) for IRC and frequency runs.                                
    The initial FCM is updated during the course of a                           
geometry optimization or saddle point search, and will be                       
punched if a run exhausts its time limit.  This allows                          
restarts where the job leaves off.  You may want to read                        
this FCM back into the program for your restart, or you                         
may prefer to regenerate a new initial hessian.  In any                         
case, this updated hessian is absolutely not suitable for                       
frequency prediction!                                                           
$GRAD group   (relevant for RUNTYP=OPTIMIZE or SADPOINT)                        
           (relevant for RUNTYP=HESSIAN when RDHESS=.TRUE.)                     
    Formatted gradient vector at the $DATA geometry.  This                      
data is read in the same format it was punched out.                             
    For RUNTYP=HESSIAN, this information is used to                             
determine if you are at a stationary point, and possibly                        
for projection.  If omitted, the program pretends the                           
gradient is zero, and otherwise proceeds normally.                              
    For geometry searches, this information (if known) can                      
be read into the program so that the first step can be                          
taken instantly.                                                                

generated on 7/7/2017