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

Mostafa Abedi mostaf... at brown.edu
Tue Apr 7 21:08:10 UTC 2020

Dear Thomas,

Many thanks for your help. I've changed the input file according to your 
suggestion. However, the temperature fluctuation is getting larger. I 
attached the corresponding files. I really appropriate if you could have 
another look into this. Thanks.



On Tuesday, April 7, 2020 at 4:14:44 PM UTC-4, tkuehne wrote:
> 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 
> TIMECON 50. More importantly, however, the dimension of your cell is too 
> large resulting in a way too low density. 
> Cheers, 
> Thomas
> Am 07.04.2020 um 21:51 schrieb Mostafa Abedi <abe... at gmail.com 
> <javascript:>>:
> 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
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