[gmx-users] Parameterizing a force field

Lee-Ping leeping at MIT.EDU
Wed May 9 20:31:17 CEST 2007

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

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

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