[gmx-developers] editing the code of the VDW and electric potentials and forces

[Asaf Farhi]

Dear GROMACS Developers

My name is Asaf.
I'm trying to implement a novel free energy calculation method and interested to do a very minor code change.
I will really appreciate help on this issue.
What I'm trying to implement in GROMACS is very simple. It's actually only one if statement that is relevant to the VDW and Electric energies and forces.

What is needed is to add for every calculation of energy and force:
If (E_VDW>Ec)
{
E_VDW=Ec;
f_VDW=0;
}
If (E_EL>Ec)
{
E_el=Ec;
f_el=0;
}

where E_VDW is the energy associated with the pair VDW interaction, f_VDW is the force associated with the pair VDW potential and Ec is a constant.
In addition I need to multiply specific VDW and electrical forces by a const (that are associated with certain atoms).

Could anyone advise me how to do this code change?

Thanks in advance,
Best regards,
Asaf
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