$FRGRPL group                                                                   
This group defines the inter-fragment repulsive potential                       
for EFP1 potentials.  It accounts primarily for exchange                        
repulsions, but also includes charge transfer.  Note that                       
the functional form used for the fragment-fragment                              
repulsion differs from that used for the ab initio-fragment                     
repulsion, which is defined in the $FRAGNAME input.  The                        
form of the potential is                                                        
      sum   A * exp[-B * r]                                                     
       i     i        i                                                         
-1-  PAIR=FRAG1 FRAG2                                                           
specifies which two fragment repulsions are being defined.                      
$FRAGNAME input for the two names FRAG1 and FRAG2 must have                     
been given.                                                                     
-2-  NAME1 NAME2 A B                                                            
     NAME1 NAME2 'EQ' NAME3 NAME4                                               
NAME1 must be one of the "NAME" points defined in the                           
$FRAG1 group's REPULSION POTENTIAL section.  Similarly                          
NAME2 must be a point from the $FRAG2 group.  In addition,                      
NAME1 or NAME2 could be the keyword CENTER, indicating the                      
center of mass of the fragment.                                                 
A and B are the parameters of the fitted repulsive                              
The second form of the input allows equal potential fits to                     
be used.  The syntax implies that the potential between the                     
points NAME1 and NAME2 should be taken the same as the                          
potential previously given in this group for the pair of                        
points NAME3 and NAME4.                                                         
If there are NPT1 points in FRAG1, and NPT2 points in                           
FRAG2, input line -2- should be repeated NPT1*NPT2 times.                       
Terminate the pairs of potentials with a "STOP" card.                           
Any pairs which you omit will be set to zero interaction.                       
Typically the number of points on which fitted potentials                       
might be taken to be all the nuclei in a fragment, plus                         
the center of mass.                                                             
Repeat lines -1- and -2- for all pairs of fragments, then                       
terminate the group with a $END line.                                           

generated on 7/7/2017