[CP2K-user] [CP2K:13090] large temperature fluctuation in NVT AIMD

[Thomas Kühne]

I was told that Packmol is very helpful: http://m3g.iqm.unicamp.br/packmol/home.shtml. 
Also, at tests/QS/benchmark (or regtests in general) you will find equilibrated water 
configurations for all sort of system sizes starting from 32 molecules. 

Greetings, 
Thomas

> Am 08.04.2020 um 20:37 schrieb Mostafa Abedi <mostaf... at brown.edu>:
> 
> You are right, I just changed the unit cell in the input file to the one that fits the structure. Is there any program/visualizer for preparing the initial state that takes the presence of periodic boundary conditions into account? 
> 
> Mostafa  
> 
> 
> 
> On Tuesday, April 7, 2020 at 5:20:12 PM UTC-4, tkuehne wrote:
> Have you also adapted the coordinates, or simply modified the cell geometry? 
> If not you may first try to carefully prepare your initial state taken the presence 
> of periodic boundary conditions into account ...
> 
> Cheers, 
> Thomas
> 
>> Am 07.04.2020 um 23:08 schrieb Mostafa Abedi <mos... at brown.edu <>>:
>> 
>> 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.
>> 
>> Best,
>> 
>> Mostafa
>> 
>> 
>> 
>> 
>> 
>> 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 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. 
>> 
>> Cheers, 
>> Thomas
>> 
>>> Am 07.04.2020 um 21:51 schrieb Mostafa Abedi <abe... 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 <http://water.xyz/>>
>> 
>> 
>> 
>> ==============================
>> Thomas D. Kühne
>> Dynamics of Condensed Matter
>> Chair of Theoretical Chemistry
>> University of Paderborn
>> Warburger Str. 100
>> D-33098 Paderborn
>> Germany
>> td... at mail.upb.de <>
>> +49/(0)5251/60-5726
>> 
>> 
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>> <water.inp><WATER-1.ener>
> 
> 
> 
> ==============================
> Thomas D. Kühne
> Dynamics of Condensed Matter
> Chair of Theoretical Chemistry
> University of Paderborn
> Warburger Str. 100
> D-33098 Paderborn
> Germany
> td... at mail.upb.de <>
> +49/(0)5251/60-5726
> 
> 
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==============================
Thomas D. Kühne
Dynamics of Condensed Matter
Chair of Theoretical Chemistry
University of Paderborn
Warburger Str. 100
D-33098 Paderborn
Germany
tdku... at mail.upb.de
+49/(0)5251/60-5726

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