[gmx-users] Re: g_x2top help

Valentina valentina.erastova at durham.ac.uk
Fri May 31 11:42:34 CEST 2013

Hi Millinda.

I know it is an old post, bt I am not sure if your defaults are correct.
This question is only because I am struggling to make CLAYff work and hence
looking around. So mb you know something I don't.

> [ defaults ] 
> ; nbfunc        comb-rule       gen-pairs       fudgeLJ fudgeQQ 
> 1               3               yes             0.5     0.5 
> ; parameters are taken from the clay force field 

The combination rule you have it is* 3*, i.e sigma & epsilon with
combination rule:
C^6_{ij} = (C^6_{i C^6_j)^{1/2} and same for C^{12}_{ij}

The paper by Cygan et al, 2004 on p. 1257, shows different combination rule
(i.e *2*).

I am also not sure if there is a need for for gen-pairs, and hence FudgeLJ
and QQ. Mine are set to default value of 1.

Thanks, V

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