[gmx-users] v-rescale - harmonic oscillator

[servaas]

Hi,

I did some experiments with a harmonic oscillator (diatomic molecule
without charge en LJ parameters) using the v-rescale thermostat. First I
ran a simulation in the NVE ensemble with a time-step of 0.0001ps, total
energy was constant here. 

Then I tried simulating the system with the v-rescale thermostat, same
time-step of 0.0001ps and tau_t=100,10,1,0.1,0.01,0.001. For none of
those simulations the effective energy was conserved. 
(effective energy should be a conserved quantity for NVT simulations
with v-rescale thermostat, JOURNAL OF CHEMICAL PHYSICS    Volume: 126
Issue: 1  Article Number: 014101    Published: JAN 7 2007 )

So what is going wrong here? Would one expect this thermostat to fail
for such system (e.g. a simple Nose-Hoover is known to fail for the
harmonic oscillator)? 


Thanks in advance,

Servaas