[gmx-users] Re: Question about embedding a force field with no torsion term

Bo Zhou zhoubo81 at gmail.com
Thu Nov 22 01:21:04 CET 2007

Thanks, Mark. Can you tell me any more in detail? I am really somewhat
confused about it. I want to cooperate this force field with oplsaa, but it
looks strange that there is not any torsion energy at all but can have 1-4
interactions. with " nrexcel=2", Do I still need 1-4 interactions made by
the procedure of genning pairs? Thanks very much.

>Bo Zhou wrote:
>> Hi all,
> >Recently I want to embed a force field (/ Chem. Mater.,/ *17* (23), 5658 
> >-5669, 2005) in gmx. In the paper, It is said that the force field 
> >parameters are consistent with GROMACS. The energy expression has a form 
> >as follows:
>>             E= E(bond) + E(angle) + E(coulomb) + E(vdW)
> >Note that there is no torsion term, I write an itp file manually and use 
> >nrexcel   2 in my molecule. I am not sure about how to deal with the 
> >1-4 interactions, because when I include with the opls force field, gmx 
> >still generates 1-4 interactions. Is it necessary for having 1-4 
> >interactions here? If necessary, how to make that force field consistent 
> >with opls ff ?

>You can make it do what you want. See chapters 4 & 5 of the manual.


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