[gmx-users] Tables with forcefield

[ms]

On 21/09/10 20:45, Sai Pooja wrote:
> I wanted to change the interactions between the Protein and Solvent so I
> tried using tables with the potential function scaled by a constant value. I
> wanted to use this in combination with forcefield parameters (charmm). I
> changed the combination rule in the forcefield.itp file from '2' to '1'
> since tables use C6 and C12 values. To test the system I started with
> default tables.
>
> When I run grompp, it generates the .tpr file successfully but in the md
> simulation using mdrun, settle does not converge. It does not converge for 1
> water molecule.
>
> If I go back to the combination rule '2' in the forcefield.itp file, I get a
> warning that using combination rule 2 with tables may generate error.
>
> With combination rule '2' and cutoff for both vanderwaals and coulombtype, i
> face no problem.

I use combination rule 1; but I also define all tabulated interactions 
for all possible *pairs* under the [ nonbond_params ] section, so the 
combination rule actually doesn't matter much.

> Does this mean that one cannot use tables with forcefield parameters?

I am not sure of understanding with question -can you clarify?

Massimo