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

[David van der Spoel]

Ryogo Sugitani wrote:
> 2007/4/5, David van der Spoel <spoel at xray.bmc.uu.se>:
>> 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.
> 
> 
> Can we still override just parameters (not the combination rule) in ver 
> 3.3.1?
> I was going to use this feature for my calculation in near future, so
> I'm a little bit concerned.

yes but according to the same combination rule as specified on top.

-- 
David.
________________________________________________________________________
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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