[gmx-users] problem with exchange probabilities in remd

David van der Spoel spoel at xray.bmc.uu.se
Sun Feb 24 09:58:49 CET 2008

> Hi all,
> I am performing a remd simulation of a peptide+water system. I have tried different temperature distributions. I am using an NVT ensemble. My temperature coupling constant is 0.1 ps.
I was going to suggest out webserver http://folding.bmc.uu.se/remd/index.php
when I realized you're doing NVT simulations (which we don't support 
yet). Why are you using NVT? It will mean your high T samples are at 
high pressure as well.

> The problem is that upon increasing the temperature difference between the two replicas more than two (290==>294), the exchange probability decreases sharply, app. to 0.03. 
> I have changed the exchange frequency in order to get a better exchange probabilities. However, it has not affected the overall exchange probabilities so much. 
> Is there anybody who has encountered such a situation?
> Thanks in advance
> Ozge Engin
> =================================
> Computational Science & Engineering
> Koc University
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David van der Spoel, Ph.D.
Molec. Biophys. group, Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205. Fax: +4618511755.
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se

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