[gmx-users] changing form of nonbonded force fields

[David van der Spoel]

Mark Abraham wrote:
> Andre Ghizoni wrote:
>> Dear gromacs users,
>>
>> I would like to know how and if it is possible to change the form of 
>> the lennard jones potential in gromacs.  What I want to do is shift 
>> the LJ function some R radius to the right for one species, i.e. 
>> f(r-R).  In effect my potential is f(r)=C1/(r-R)^12-C2/(r-R)^6, where 
>> r is the true distance between particles.  If it is not possible to do 
>> that, I would appreciate any suggestions on approximating this 
>> function with other functions that gromacs uses.
> 
> If I recall correctly, you might be able to do this with a table lookup 
> for LJ, however at the moment you can't use the table for only one 
> species. Some source code hacking might change that fairly readily.
> 
actually you can, you can define one table per interaction in the matrix.

-- 
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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