[gmx-developers] nose hoover thermostat induces resonance

[David van der Spoel]

Hi,

we are simulating some liquids with OPLS and GAFF using Leap frog 
integrator, Nose Hoover (tau_T = 1 ps) and Parrinello Rahman (tau_P = 1 
ps) and find that in some cases the Angle potential energy couples to 
the Temperature. This leads to a resonance where the temperature 
fluctuates with an amplitude of roughly 150 K (for 216 molecules) and 
the system freezes.

Could this be a side effect of the coupling constants?

Maybe the angle frequency matches the tau_T?

Any other clues?

-- 
David van der Spoel, Ph.D., Professor of Biology
Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205. Fax: +4618511755.
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se