[gmx-developers] Brainstorming ideas for minimally painless incorporation of an MC barostat (later MC moves in general)

Shirts, Michael R. (mrs5pt) mrs5pt at eservices.virginia.edu
Thu Jul 17 16:49:29 CEST 2014

Hi, all-

> I understand that the virial is not needed for the pressure scaling
> itself, but it will usually be calculated for reporting at a scaling
> step, so we need to get it right, also with constraints.

Sure, the exact details depend on the way the bookkeeping is done, but if
the forces are calculated in the energy used for the MC barostat, then one
might as well get the virial right as well in that step.  I'll need to
think about it a little more, but as far as I can tell, the configuration
at which the forces are calculated is part of the ensemble of interest,
therefore the pressure calculated there can be used.  But then one starts
to get into the weeds of where different quantities are calculated and
perhaps best to avoid that for now.

I do think the minimal thing to do have the call with the transformed
coordinates for accept/reject be as similar to the normal call as possible
for simplicity.  Optimization for other criteria can be done later.

> If we don't want to calculate the force 3x when a MC step is rejected,
> we can directly reuse the storing mechanism implemented in minimize.c.

Interesting.  What would need to be done to generalize that mechanism?

Michael Shirts
Assistant Professor
Department of Chemical Engineering
University of Virginia
michael.shirts at virginia.edu

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