[gmx-users] solvent temperature

imparato at na.infn.it imparato at na.infn.it
Mon Mar 9 13:43:07 CET 2009

Dear users
I have the following problem and was wondering if anyone can help me.
I'm trying to set up some SDS + water simulations, with Beredsen
temperature coupling
tcoupl = Berendsen
tc-grps = system
tau_t = 0.1
ref_t = 300

when I use the rigid solvent topology
#include "spc.itp"
and try to sample the system temperature with
g_traj -f full -s full -ot temp.xvg -xvgr
if I consider separately the temperature of the SDS and the Solvent, the
SDS has the correct temperature (around 300 K), the solvent has a wrong
temperature (around 200 K).
The system as a whole has a wrong temperature (around 210 K).

If I use the flexible solvent topology
#include "flexspc.itp"
then the temperature of the solvent is 300K, as expected.

I have the same problem if I couple separately the SDS and the solvent to
the termostat
Tcoupl              =  Berendsen
tc-grps		    =  SDS  SOL  NA+ CL-
tau_t               =  .1  .1   .1  .1
ref_t               =  300  300  300 300

Did I do something wrong, or has this to do with the constraints in the SCP

Thank you in advance

Alberto Imparato

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