[gmx-users] tau-p value

[Mark Abraham]

On 27/02/2012 6:35 PM, zhongjin wrote:
> Dear GMX users,
>  I find that tau_p value is very important to NTP simulation, when I 
> use tau_p  = 1ps, the default value, the box change a lot, only when I 
> use tau_p = 10 ps, it is OK.
> ; Pressure coupling
> Pcoupl                   = Parrinello-Rahman
> Pcoupltype               = semiisotropic
> nstpcouple               = -1
> ; Time constant (ps), compressibility (1/bar) and reference P (bar)
> tau-p                    = 10
> compressibility          = 0  4.5e-5
> ref-p                    = 1.0 1.0
> ; Scaling of reference coordinates, No, All or COM
> refcoord_scaling         = No
> ; Random seed for Andersen thermostat
> andersen_seed            = 815131
> So How to set up tau_p value, is 10 ps acceptable? My system cotain a 
> CNT membrance in it.
>

Such values during equilibration are often different for those for 
production runs. You should not be using P-R during equilibration, as 
you will see in the relevant manual section.

Mark
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