[gmx-users] Tau_t values

David van der Spoel spoel at xray.bmc.uu.se
Fri Mar 3 14:17:25 CET 2006

Fernando Mattio wrote:
> Dear all,
> I have performed simulations in which my reference pressure and 
> reference temperature values were 1 bar and 263 K. I don´t have many 
> knowledges about the Tau_t and Tau_p values, so I performed many 
> simulations to evaluate these parameter in my system, in order to get 
> pressure and temperature close to these values. I observed in the forum 
> that most users uses as standard tau_t = 0,1 and tau_p = 1,0, but the 
> values that I obtain in my case are far away from the reference ones 
> when I use these "standard" values.
> I made tests with tau_p = 1, and tau_t I varied from 0,500 until 0,001. 
> Only close to 0,005 I have pressure and temperature close to the 
> reference values. But I don´t know if it is all right to work with so 
> low values for tau_t. Does anybody has experience with such low values? 
> What would be the consequences by using these values?
> Thank you once more for your attention,
> Best regards,
> Fernando Mattio

I suggest you read the original paper:
   author =	 "H. J. C. Berendsen and J. P. M. Postma and
                   A. Di{N}ola and J. R. Haak",
   title =	 "Molecular dynamics with coupling to an external
   journal =	 "J. Chem. Phys.",
   year =	 "1984",
   volume =	 "81",
   pages =	 "3684--3690",
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David van der Spoel, PhD, Assoc. Prof., Molecular Biophysics group,
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,  	75124 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se

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