[gmx-users] What is the difference between joined and seperate tem coupling?

Xavier Periole x.periole at rug.nl
Mon Nov 28 11:46:09 CET 2005

Tanping Li wrote:

>Dear all,
>I am simulating the hyrdation issume of protein under
>NVT  condition. We use Gromos96 force field. I noticed
>that in the tutorial mdp file, the protein and solvent
>are tem coupled seperately. Could I use the global
>tem-coupling? Is there any real difference between
>Thank you very much for your reply.
I wanted to go back to a series of email concerning the use of
one/two temp baths to couple the solute and solvent. This is
an important matter that people doing MD should be aware of.

The use of two baths is necessary for different reasons, which
are mainly that the use of only one bath will result in a
significant loss of temperature of the solute. This is due to:
1) Upon the propagation of the system numerical errors occur
(always resulting in an increase of the temperature). Because
the solvent is the major contributor to the interactions or forces
in the system its temperature will increase and to compensate
the solute will loose temperature.
2) the use of constraints will also decrease the temperature of the
solute, more than for the solvent.


 Xavier Periole - Ph.D.

 Dept. of Biophysical Chemistry / MD Group   
 Univ. of Groningen
 Nijenborgh 4
 9747 AG Groningen
 The Netherlands
 Tel: +31-503634329
 Fax: +31-503634800
 email: x.periole at rug.nl
 web-page: http://md.chem.rug.nl/~periole

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