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Re: [lammps-users] feature request: hybrid monte carlo
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Re: [lammps-users] feature request: hybrid monte carlo


From: Steve Plimpton <sjplimp@...24...>
Date: Fri, 7 Jul 2017 08:42:24 -0600

Efrem - long ago I wrote a sample "hmc" command in collaboration
with Ed Maginn (UND) to try out HMC in LAMMPS.
We were never totally happy with how it worked, so
it was never released.  I will send you a small
tarball with the code (single command) and doc
page.

It would be great if you want to modify/test it and
see if you can make it work and release it.

Steve

On Fri, Jul 7, 2017 at 5:57 AM, Efrem Braun <efrem.braun@...297...> wrote:
Hello,

I'd like to submit a feature request for Hybrid Monte Carlo (HMC) simulations. At present, one can do mixed MD/MC using a combination of 'fix gcmc' and a time integration fix. However, there's no way to accept/reject the MD moves that take place between the steps when 'fix gcmc' is invoked. I believe that such accept/reject rules are formally necessary to provide detailed balance for proper sampling. (Velocity re-randomization is also necessary, but this can be currently implemented by the user looping between 'velocity create' and 'run' commands.)

I'm not sure of the best implementation for this feature. I think it'd probably be best to add a keyword to 'fix gcmc' to do this, and then LAMMPS would save the state at the end of the Monte Carlo moves and compare it to the energy of the state when the Monte Carlo moves next begin.

I might be able to implement this myself, but I wanted to check first to see if this feature is already being developed and to see what else the developers or other users thought about this.

Efrem Braun

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