[gmx-users] Wrong pressure with rigid water

[Mark Abraham]

Hi,

The solvent models are designed to be rigid, use flexible versions only if
you know why they will be a good model for you.

Measuring pressure can take nanoseconds, but we don't have enough
information to know what you've done and its error estimates.

Mark

On Mon, 14 Nov 2016 17:21 Sudip Das <das.sudip37 at gmail.com> wrote:

> Dear All,
>
> I am simulating a protein in water with GROMOS96 force field (gromos54a7)
> and SPC/E water model. After minimization followed by NVT equilibration, I
> performed 2ns of NPT equilibration. From the converged box length I have
> taken the average value and set the box length (in npt_equilibrium.gro
> file) to that value and used this for NVT production run.
>
> In the production run, temperature, potential and total energies are
> reasonable, whereas the pressure is behaving weirdly. I have started the
> NVT production run with 1 bar pressure.
>
>
> NVT production run with flexible water (define = -DFLEXIBLE): P = 1 to 5
> bar
>
> NVT production run with rigid water: P = 750 to 780 bar
>
>
> Did anyone encountered this kind of problem? I would appreciate your kind
> help in resolving this.
>
> Best regards,
> Sudip
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