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Hi,<br><br>I think you are talking about two different concepts.<br>At the moment of switching the replicas, the potential energy<br>does not change, because the force field is temperature indepent.<br>This is what Chris meant.<br>As the system evolves in time, the potential energy will go up<br>when a replica is switched to a higher temperature.<br><br>Berk<br><br>> Date: Thu, 4 Dec 2008 03:19:17 +1100<br>> From: Mark.Abraham@anu.edu.au<br>> To: gmx-users@gromacs.org<br>> Subject: Re: [gmx-users] REMD problem in concept<br>> <br>> chris.neale@utoronto.ca wrote:<br>> > dG=dH-TdS<br>> > <br>> > so as T increases, so does the entropic contribution to the free energy <br>> > (=available energy). The potential energies stay the same when using a <br>> > temperature-independent forcefield (like all of the ones that come with <br>> > gromacs).<br>> <br>> That's not quite right. The average total energy (H, above) increases <br>> with T, and the equipartition theorem requires that for a typical MD <br>> system in thermal equilibrium, some of that energy must go to increased <br>> average PE. The form of the forcefield doesn't change, of course. This <br>> KE-PE-TE behaviour can be readily observed in an REMD simulation and is <br>> documented in various graphs in various REMD papers.<br>> <br>> > Your system will easily cross barriers on the order of KbT and thus <br>> > barriers are more easily crossed at higher temperature.<br>> ><br>> > Nearly every RE paper has an introductory section that goes over these <br>> > topics in more or less detail. I suggest that you read the introduction <br>> > and theory sections of about 10 of them and you should by then <br>> > understand it very well.<br>> <br>> Yep, agreed.<br>> <br>> Mark<br>> _______________________________________________<br>> gmx-users mailing list gmx-users@gromacs.org<br>> http://www.gromacs.org/mailman/listinfo/gmx-users<br>> Please search the archive at http://www.gromacs.org/search before posting!<br>> Please don't post (un)subscribe requests to the list. Use the <br>> www interface or send it to gmx-users-request@gromacs.org.<br>> Can't post? Read http://www.gromacs.org/mailing_lists/users.php<br><br /><hr />Express yourself instantly with MSN Messenger! <a href='http://clk.atdmt.com/AVE/go/onm00200471ave/direct/01/' target='_new'>MSN Messenger</a></body>
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