[gmx-developers] question on PV term

[Berk Hess]

Hi,

I would say there is not much point in this quantity.
One would not need it often, and if one would, you can simply
calculate it using the volume in the energy file.

Berk

Michael Shirts wrote:
> The PV term computed using pressure control is calculated as:
>
> pv = vol*enerd->term[F_PRES]/PRESFAC;
>
> i.e. the volume times the instantaneous pressure.  It's not clear to
> me there is a reason to compute this quantity. In the partition
> function, one uses P_ext V, where P is the external pressure that the
> system is maintained at, in the same way that when computing E/kT, you
> use the external temperature, not the instantaneous average of kinetic
> energies.
>
> It could be that there is a use for this quantity, but otherwise, I'd
> suggest changing it to
>
> pv = vol*trace(ir->ref_p)/(DIM*PRESFAC)
>
> or the tensor equivalent.
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