[gmx-users] Regarding tc-grps

Peter Kroon p.c.kroon at rug.nl
Thu Sep 29 17:18:57 CEST 2016


please see http://www.gromacs.org/Documentation/Terminology/Thermostats

The number of molecule types (what you call groups?) in your .top file
are not relevant for the number of tc groups you make.

You need to make sure your system obeys a boltzmann distribution (or
maxwell? I'm not sure). In principle a single temperature coupling group
is always enough, but the exchange of thermal energy between i.e. a
protein and the surrouding solvent may not be efficient enough to make
sure that this is true. In such a case people use two (or more)
temperature coupling groups.

To sum up: your system as a whole needs to obey a certain distribution
of kinetic energy. In addition, every "subsystem" (i.e. protein or
solvent or any combination thereoff) needs to obey such a distribution
as well.

In your case, I think a single tc group (System) should be enough.



On 29-09-16 16:31, Anurag Dobhal wrote:
> Dear Gromacs users,
> I am simulating a polymer chain without any solvent using OPLS AA force
> field, how many tc-grps  should I put in the .mdp file ? as there is only
> one 1 group in the topol.top file.
> Thank You
> *Anurag Dobhal*
> *Graduate Student (Bioprocess Technology)*
> *Institute of Chemical Technology, Mumbai*

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