[gmx-users] torsion potential with 7 parameters

[Ángel Piñeiro]

Hi all,
anyone knows how to use (in gromacs) a potential of the type:

U_tors(phi_ijkl) = Sum_n 1/2 k_n [1-cos(n phi_ijkl)]

with n going from 1 to 7?

as far as I saw only the Ryckaert-Bellemans with 6 parameters and a
periodic function are implemented in gromacs. Chapter 4 says something
about this subject and it explains how to translate OPLS in R-B but it
seems that 7 parameters are not included

I am trying to use the force field for perfluoroalkanes published by
Borodin et al in JPCB (106) 2002, 9912.

Thanks in advance for the help,

Angel Piñeiro.