[gmx-users] Avg. Volume in NPT by Small Coupling Time

[Mark Abraham]

Hi,

I think that's fine for rapidly forcing the volume to be close to the right
equilibrium value, with low fluctuations. Then switch to gentler NPT (or
constant-volume) for making a proper observation of the pressure.

Mark

On Thu, Nov 6, 2014 at 4:44 PM, Johnny Lu <johnny.lu128 at gmail.com> wrote:

> Hi.
>
> How to get an accurate average volume for a system, such that the pressure
> will be at 1 bar in a subsequent NVT run using this average volume?
>
> Is it ok to use Berendsen barostat with a very small time constant (0.2 ps)
> ?
> (At first I picked 0.1ps, gromacs 4.6.7 told me to use at least 0.2 ps).
>
> I was hoping that a smaller time constant would allow the simulation to
> sample the volume more frequently and Berendsen barostat would help the
> system to converge to the correct average volume faster.
>
> What are the possible draw backs?
>
> So far (2 ns), I see that the pressure fluctuation is smaller than a PR
> barostat.
>
> It seems to be fine to use Berendsen barostat for this purpose ( [
>
> https://mailman-1.sys.kth.se/pipermail/gromacs.org_gmx-users/2011-February/058453.html
> ]
> )
>
> Thank you again.
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