[gmx-users] interaction forces

[Martin Rex]

On Thu, 7 Oct 2004, Berk Hess wrote:

> 
> >
> > >>is it posible to apply two different interaction potentials to one atom
> > >>depending on the counterpart? For example OW-OW 6-12 LY and OW-NA 6-10
> > >>LY.
> >
> > >If you only need OW-OW and OW-NA it is possible using the user tables.
> > >But with one extra interaction, for instance NA-NA it becomes impossible.
> >That is all I need. But how is it done? Is it possible to define a
> >user-table that only affects a certain atom combination like OW-NA?
> 
> You can (mis-)use the user-tables.
> There are separate tables for dispersion and repulsion.
> You can fill the one for the dispersion with a 6-12 LJ with the correct 
> sigma
> and the one for repulsion with a 6-10 LJ with the correct sigma
> Then for OW-OW you should set the appropriate c6 and c12=0
> and for OW-NA the approprate c12 and c6=0.
> The manual describes the format of the user tables.

Can I use coulomtype=PME and just vdw=user? And if so, do I have to leave 
the coulomb part in the table empty or set them to zero? 

Thank you very much.

Martin
> 
> Berk.
> 
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