[CP2K-user] [CP2K:13078] large temperature fluctuation in NVT AIMD

Thomas Kühne tku... at gmail.com
Tue Apr 7 20:14:37 UTC 2020

Dear Mostafa, 

you are relying on the default values for the thermostat. For such a small system (the fluctuations scale with the sqrt 
of the number of particles), a strong coupling is necessary. Try for instance REGION MASSIVE, TYPE CSVR and 
TIMECON 50. More importantly, however, the dimension of your cell is too large resulting in a way too low density. 


> Am 07.04.2020 um 21:51 schrieb Mostafa Abedi <abedimo... at gmail.com>:
> Hi Everybody,
> I am trying to do NVT AIMD simulations for a system consisting of 16 H2O molecule. Strangely, the temperature fluctuation is very large (see attached "WATER-1.ener" file). I know a little bit temperature fluctuation is acceptable, but mine is really large. This is the first time I am trying CP2K for doing AIMD and not familiar with structure of the input file. Maybe something is wrong or missing in the input file (see attached "water.inp" file). I should say I've already done this calculation with ORCA for non-periodic water system. Now, I want to see the effect of periodicity with cp2k. Any help would greatly appropriated. Many thanks.
> Best,
> Mostafa 
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> <WATER-1.ener><water.inp><water.xyz>

Thomas D. Kühne
Dynamics of Condensed Matter
Chair of Theoretical Chemistry
University of Paderborn
Warburger Str. 100
D-33098 Paderborn
tdku... at mail.upb.de

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