[gmx-users] (no subject)

[David van der Spoel]

rob yang wrote:
> Hello,
> I've got a rudimentary question about gromos torsion parameters.
> 
> the gromos parameter is of the following format:
> gd_1           2.67             -1.0            1
> name      force constant  phase shift    multiplicity
> 
>> From the gromos paper, they've listed the torsion terms as 
> K*[1+cos(phaseshift)cos(multiplicity*dihedral)
> 
> In a given .top file, one would parameterize the torsion of i, j, k, l by:
> i j k l gd_1
> 
> so my question is that: does that mean for any torsion, there's only 
> *one* term associated with it in the gromos forcefield? In contrast,  
> oplsa allows up to 6 terms in the following form:
> V1/2(1+cos(x))+V2/2(1-cos(2x)) + V3/2(1+cos(3x))...
> 
Yes that's correct, although you could in principle add multiple 
torsions I think.

> 
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-- 
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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