[gmx-users] compressibility value for SPC water

[Mark Abraham]

> Dear all,
>
> I read from the mailing list archives, that it is not just the value of
> tau_p but the ratio of compressibility to tau_p which matters in Berendsen
> presure coupling.  I am using SPC water as the solvent. Is there any ideal
> value for compressibility to be used for SPC water?

Not that I'm aware of, but you could look at the literature for the
development of SPC water.

> i have used a value of
> 4.5e-5, and a tau_p of 1.0 ps, and my pressure coupling is isotropic.
>  Should the tau_p value be increased or decreased to get a pressure
> average
> closer to ref_p?

Smaller tau_p "tightens" the coupling of system pressure and ref_p, so
that your pressure average will be closer to ref_p. You could of course
try different values and see for yourself... :-)

Mark