[gmx-users] interaction forces

[Berk Hess]

>
> >>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.

Berk.

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