[gmx-users] modify C6 directly in FF using sigma and epsilon

David van der Spoel spoel at xray.bmc.uu.se
Thu Apr 5 21:03:45 CEST 2007

Ryogo Sugitani wrote:
> David,
> How about adding [ nonbond_params ] in your ff???nb.itp file
> as shown in p.88 of the user's manual?
> I believe it will override the default vdw interaction for that
> particular atom-type pair.
> (Assuming you want to use combination rule #1 just for that atom-type pair)
> If I miss your point, please disregard this...
In gromacs 3.3 it will still use the same combination rule. However, in 
older versions, possibly 3.2.1, this would work: use sig/eps for 
generating a matrix and overriding it with C6/C12. We took that out 
because it is hard to explain, and we thought it was unnecessary...

David van der Spoel, PhD, Assoc. Prof., Molecular Biophysics group,
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,  	75124 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se

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