[gmx-users] Parameterizing a force field

[Lee-Ping]

Hi there,

I'd like to fit a set of force field parameters (100+) to a set of
several ab initio force calculations.  I've noticed that ffscan is
tailored to this purpose, but I don't know how to use it, so I wrote a
script that tries to fit the force field parameters using some numerical
optimization techniques.

Every time I vary one of the force field parameters, I need to call
grompp and mdrun and run a single-point calculation to get the force.
(a small detail: I use "rerun" so I only need to call mdrun once for a
batch of geometries with the parameters fixed).  The optimization
techniques all work by varying the force field parameters and comparing
the forces that come out; thus, I need to call grompp and mdrun many
thousands of times, with the only thing modified being the force field
parameters.

It turns out that repeatedly calling mdrun and grompp uses up a lot of
computer resources, and takes up most of the time involved in the
optimization.  Is there a method out there for rapidly running several
force calculations on the same molecular geometry/topology, with only
the force field parameters modified (perhaps with only a single call of
grompp or mdrun)?

Thanks a lot!!

- Lee-Ping