Re: [AMBER] Question about volume when switching from NPT to NVE ensemble

From: David A Case <case.biomaps.rutgers.edu>
Date: Thu, 24 Apr 2014 15:31:35 -0400

On Thu, Apr 24, 2014, Quynh Vo wrote:
>
> My question is that when I make the switch, what volume information will
> be used by amber for the constant volume? Is it the volume that was
> last written out to the restart file?

Yes.

> If that is the case, then what
> will happen to the density of my system, as during NPT run, the density
> fluctuated with volume. 
> Or my concern would be dismissed if the last volume that is written out
> to the restart file is the average volume over the whole equilibration.

You can manually edit the restart file to put in whatever box dimensions you
want, e.g the average over the last N steps of the NTP run. One would
generally not want the average over the whole equilibration.

One "trick" that we often use: set ntp=1, but taup=9999999. This will allow
you to monitor the pressure during what is still a constant volume run.

...dac


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Received on Thu Apr 24 2014 - 13:00:02 PDT
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