[gmx-users] temperature explosion...
jake at ncsa.uiuc.edu
Tue May 13 17:48:01 CEST 2003
Another thing that will influence this is how frequently you update the
pair lists for the direct non-bonded interaction. The only way to make the
system truly conservative is to update the pair list every time
step. Otherwise I think you will get spurious heating of the sort that you
describe in constant energy calculations.
At 02:29 PM 5/12/2003 +0200, you wrote:
>>On Fri, 2003-05-09 at 17:50, Giorgos Karvounis wrote:
>>>I want to simulate a pentapeptide at 360 K without Tand P coupling. I
>>>first do an equilibration run , starting from a 360K velocity and T / P
>>>coupling for 100 ps. After that, i switch the coupling and continue the
>>>same run . I monitor the temperature and it seems that it explodes, from
>>>358 to 491 to 651 K every 10000 steps. Is this suppose to happen? Shall
>>>i perform the equilibration longer?
>>>Is it possible to keep the temperature/energy constant without using
>>yes, use PME.
>You can have a look at J. Comput. Chem. 20, 786-798 (1999) for what
>size of energy drift you can expect at different timestep. Note these
>simulations were done with shifted potentials, to eliminate the cut-off
>noise (hence Davids suggestion for PME, which does nearly as good),
>and in double precision. It depends on how long you want the temperature
>to remain constant, and why you want to run without temperature coupling.
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Eric Jakobsson, Ph.D.
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Professor, Beckman Institute for Advanced Science and Technology
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