[gmx-users] changing form of nonbonded force fields

[Mark Abraham]

Andre Ghizoni wrote:
> Dear gromacs users,
> 
> I would like to know how and if it is possible to change the form of the 
> lennard jones potential in gromacs.  What I want to do is shift the LJ 
> function some R radius to the right for one species, i.e. f(r-R).  In 
> effect my potential is f(r)=C1/(r-R)^12-C2/(r-R)^6, where r is the true 
> distance between particles.  If it is not possible to do that, I would 
> appreciate any suggestions on approximating this function with other 
> functions that gromacs uses.

If I recall correctly, you might be able to do this with a table lookup 
for LJ, however at the moment you can't use the table for only one 
species. Some source code hacking might change that fairly readily.

Mark