[gmx-users] Amber OPLS dihedral conversion to GROMACS RB

[Anton Feenstra]

DaJustice1 at aol.com wrote:
> Dear GMX Users,
>  
> I am attempting to convert Amber OPLS dihedral parameters to GMX RB 
> parameters, but I’m having some trouble.   I have searched through the archives and 
> found replies about the same problem.   The replies state that the conversion is 
> described in the GMX Users manual.   I have read the force field section 
> covering dihedral conversion to RB, but I still am not sure how to proceed.   Amber 
> OPLS has multiple definitions for dihedrals using different PN, but GMX only 
> has one line containing the six RB parameters C 0-5.   If someone in the list 
> has experience with these conversions, please enlighten me.

IIRC, the trick is *not* to use the Gromacs RB dihedrals, but in stead
define *multiple* 'normal' Gromacs dihedral potentials with different
multiplicities. I'm not sure if all versions (distributions) of Gromacs
actually support multiple dihedrals, they probably do in the .top (i.e.
for grompp), but may not in the .rtp (i.e. for pdb2gmx).


-- 
Groetjes,

Anton
  _____________ _______________________________________________________
|             |                                                       |
|  _   _  ___,| K. Anton Feenstra                                     |
| / \ / \'| | | Dept. of Pharmacochem. - Vrije Universiteit Amsterdam |
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