[gmx-users] Highest possible temperature in NPT?

[pascal.baillod at epfl.ch]

Dear community, 
 
I am trying to perform some wild REMD tests, and see the effect of very high 
temperature on a solvated 100-residue protein.. ("hottest" replica temperatures 
of 500-1000K). So far, the simulations would crash whenever using the NPT 
ensemble.. temperatures would remain correct but the volumes would grow too 
big. In NVT, I can apparently go as high in temperature as I wish. I suppose I 
could get it to work for NPT as well, provided a massive increase of the tau_p 
pressure time coupling constant. I found no info on that in the mailing list 
and was wondering if anybody has experience on 
 
a) How much can I increase tau_p without getting too unphysical (under the 
assumption there is still anything physical at >500K!)? I read that the 
important thing is to conserve the compressibility/tau_p ratio.. should I 
change tau_p AND compressibility values for higher temperatures? 
 
b) Which, of the Berendsen and Parinello-Rahman barostats, would be more suited 
for such high temperaure NPT simulations? 
 
Thank you very much for your help!! 
 
Pascal 
 
 
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Pascal Baillod (PhD student)  
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Swiss Federal Institute of Technology EPFL	        Tel: +41-(0)21-693-0322 
Institute of Chemical Sciences and Engineering ,	Fax: +41-(0)21-693-0320 
Laboratory of Computational Chemistry and Biochemistry	pascal.baillod at epfl.ch 
Room BCH 4121, Avenue Forel,	                        http://lcbcpc21.epfl.ch 
CH-1015 Lausanne	 
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