[gmx-users] impropers in oplsaa

[Erik Lindahl]

mojtaba alaei wrote:

> Dear All
>
> Can I use impromer dihedral force field in gromacs-3.1.4?


Sure - check the manual and the ffgmx* or ffG96* force fields for details.
OPLS doesn't use improper dihedrals, but normal dihedrals with 
periodicity 2 and a higher force constant for planar groups.
It doesn't use any impropers at all for chiral centers (not necessary 
with all atoms present). You can of course still add improper
dihedrals in your topology, but it would be against the normal OPLS setup.

Cheers,

Erik