[QE-users] temperature fluctuations in NVT ensemble - Car-Parinello calculations

Zahra Nourbakhsh z.nourbakhsh at gmail.com
Fri May 15 00:51:28 CEST 2020


Dear experts,

I am doing CPMD calculations for water in the NVT ensemble where the ionic
temperature is controlled using Nose-Hoover thermostat.
After several femtoseconds, the system finds its equilibrium, and the
temperature oscillates around the intended temperature. I see that using
different pseudopotentials or vdw-correction, the temperature changes
around the equilibrium are different.
I know these fluctuations come from the limited size of the system and they
will be reduced by increasing the number of molecules in the system;
however, my question is that is there any limitation on the acceptable
value for  (T_max-T_0)/T_0 or (T_0 -T_min)/T_0?  T_0 is the considered
temperature.
And is there any parameter or any way to reduce these fluctuations?

Thank you very much in advance.
Yours sincerely,
Zahra Nourbakhsh
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