[gmx-users] Pressure coupling for anisotropic system

[Erik Lindahl]

Hi,

If you are doing full anisotropic coupling you will need six values 
each for reference pressure and compressibility. The first three 
correspond to the diagonal of the tensor, and the other three to the 
off-diagonal elements. A normal compressibility (water) is in the order 
of 5e-5, but it depends somewhat on your system. Unless your system can 
support shear/stress you should use pressure=0 for the off-diagonal 
elements.

Tau_p still controls the timescale of the coupling, which depends on 
your system. Most people use from 1 to 20 (picoseconds).

Cheers,

Erik




On Monday, October 6, 2003, at 04:31 AM, hiroo_fukunaga at fujifilm.co.jp 
wrote:

>
> Hello gmx users,
>
> I do not know how to make .mdp file for the simulation of an 
> anisotropic
> system,
> e.g. crystal (a.eq.b.ne.c, alpha=90, beta=90, gamma=120).
> A part of the .mdp file is as follows.
>
> Tcouple            = nose-Hoover
> ref_t                 = 300
> tc_grps             = system
> tau_t                = 0.1
> Pcouple           = Parrinello-Rahman
> Pcoupletype     = anisoitropic
> tau_p               = ???
> compressibility = ???
> ref_p               = 1.0
>
> What  values and how should I input for tau_p and compressibility.
>
> Thank you.
>
> Hiroo Fukunaga
>
>
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