[gmx-users] change coloumb interaction

[Sang-Min Park]

Dear all,

I want to change (for example : 2 times the 'normal' value) only the 
coloumb interaction between the solvent and a small peptide molecule. On 
the other hand the interaction  SOL-SOL and 
peptide-peptide should be according to the standard given parameters of 
GROMACS.

The change of the charges would be not the solution, because this would 
cause also a change in the SOL-SOL and pep-pep coloumb interaction.

For example for the LJ Potential the change of the interaction potential 
(only the interaction) can be done easily when one scale the nonbonded 
interaction parameters. Furthermore one has to define some new atomtypes..

For the coulomb interaction I think I have to modify the source code 
concerning the ewald summation, e.g. I have to multiply all contributions 
SOL-PEP with a scaling factor a.

So related to the mentioned problem I have the following question:

In which file and where there I have to make the changes ?

Thank in you in advance
Sang Min