[CP2K-user] [CP2K:21121] Help with Temperature Fluctuations in MD

[Rishikanta Mayengbam]

Hi Lucas,

Thanks for your detailed analysis and suggestions. My system consists of an 
organic molecule above a CsPbBr₃ slab. The initial structure for MD was 
taken from a VASP-optimized configuration. However, I may need to 
reoptimize it again in CP2K before running the MD simulation.

I'll try your suggestions and see if they improve the results.

Thanks again for your help!

On Friday, February 7, 2025 at 12:11:29 AM UTC+8 Lucas Lodeiro wrote:

> Hi,
>
> From your ener file it is clear that there is some high reorganization or 
> reaction for your system... the potential energy falls from -6631 to .6669 
> Hartrees, 38 Hartrees of fall is not due to the normal AIMD oscillations or 
> thermal effects. Did you optimize your slab structure before to run the MD?
> Taking into account the atoms listed on the input you are simulating a 
> perovskite Cs/FA/MA-PbBr_3, which has high reorganization at the surface, 
> w.r.t. the bulk structure, when the cleavage to construct the slab is done. 
> For Cs/FA/MA-Br surface, could be organic cation rotations, and for PbBr 
> surface there is a high reordering due to surface states/dangling bonds, 
> and also rotations of organic cations. Here you can read a paper dedicated 
> to this features of perovskites: 
> https://pubs.acs.org/doi/full/10.1021/acsomega.0c04420
>
> Also, in your input, at fixed atom section you can use (if the complete 
> list of numbers from 1 to 483 is needed): LIST 1..483
>
> Regards - Lucas
>
> El jue, 6 feb 2025 a las 10:30, Rishikanta Mayengbam (<
> rishikant... at gmail.com>) escribió:
>
>> Dear users, 
>>
>> I’m running an NVT MD simulation for a molecule on a slab (vacuum in y 
>> direction) in CP2K at 300 K using a Nose-Hoover thermostat, but I’m seeing 
>> extreme temperature fluctuations (up to 50,000 K within a few steps). 
>>
>> Do you have any suggestions on how to stabilize the temperature? Any 
>> insights would be greatly appreciated.
>>
>> Best,
>> Rishikanta
>>
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>

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