[gmx-users] parrinello-rahman to wrong pressure

[Erik Lindahl]

Hi Michael,

Send me the necessary files as a tarball and I'll look into it - but it 
might take a week or so before I find the time :-)

Cheers,

Erik

On Thursday, October 16, 2003, at 05:12 AM, Michel Cuendet wrote:

>
> Hi gmx fans,
>
>   After heating up my system with a slightly oversized fixed box, I 
> start the equilibration with a barostat (parameters below). How is it 
> possible that parrinello-rahman expands the box and maintains an 
> average pressure of about -1900 bar (over 100's of picoseconds) ? All 
> conditions identical, the berendsen barostat decreases the box size 
> and then keeps a reasonable pressure. It seems that the final pressure 
> for parrinello-rahman depends on the size of the system : with more 
> water, it reaches a pressure of -2400 bar.
>
>   Has anyone an explaination ?
>
>   Thanks,
>
> Michel
>
>
> tcoupl                   = nose-hoover
> tc-grps                  = Protein
> tau_t                    = 0.1
> ref_t                    = 300.0
> Pcoupl                   = berendsen  /   parrinello-rahman
> tau_p                    = 1.0
> compressibility          = 4.5e-5
> ref_p                    = 1.0
>
>
>
>
>   PS: My previous message about thermostats in presence of a frozen 
> group has still not been replied.
>
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