[gmx-users] how to extend the order of Ryckaert-Bellemans dihedral

[Makoto Yoneya]

Hi all:

I'm planning MD of a molecule with fluorocarbon chains with united CFn.
Since the system size and each molecule itself rather large,
I need united CFn instead of explicit F atoms.
Complex torsion potential of CF2-CF2-CF2-CF2 needs more higher order than
the Ryckaert-Bellemans (up to 5th) potential (e.g. up to 7th or even
12th see Cui et al. Fluid Phase Equilibria 146 '98 51-61 etc.).
How can I extend the order of the Ryckaert-Bellemans type dihedral
function (e.g. which routines in GROMACS source code needs changes?).

Thank you for advance.

Makoto Yoneya
Yokoyama Nano-structured Liquid Crystal Project.
Tsukuba, Japan