[gmx-users] fitting dihedral angle function parameters using gromacs

[fay4 at pitt.edu]

Dear Gromacs developer:

I am asking for your help about fitting a dihedral angle parameters using
gromacs md simulation. One article (link:
http://www.mpip-mainz.mpg.de/~andrienk/journal_club/opls.pdf) says that
fitting a dihedral angle potential parameters needs three steps: 1)
perform ab initio calculation; 2) do md simulation by setting the dihedral
angle parameters to zero; 3) fit all the parameters by comparing the md
energies and ab initio energies.

I am now working on a dihedral angle fitting and I have done step 1. But I
don't know how to do step 2 and 3. For example, if I want to fit a
CT-CT-CT-CT dihedral angle for butane, how do I prepare for my *.mdp file,
and after md simulation, how to fit the md energies to the ab initio
energies?
Would you please help me?

Thank you.