Temp droping i n NVE ensembles

[shamimul Ahsan]

Dear cp2k users,

I am do ab initio MD in NVE ensembles for water faujasite (zeolite NaY) system. I fixed the temp at 298K. But during the simulation temperature drops and fluctuates around 150K. Ideally, it should fluctuate around 298 in NVE ensembles. I have attached my input file. Can anybody go through it and suggest something? Any suggestion will be highly appreciated.  

With regards

Shamimul Ahsan

[Thomas Kühne]

Dear Shamimul Ahsan, 

the systems needs to be equilibrated in the canonical NVT ensemble first, 

ideally with massive thermosetting. If fo instance your initial geometry originates 

from a geometry optimization, the kinetic energy is in the beginning converted 

into potential energy to yield an equilibrium structure at 298 K, instead of 0 K. 

The same may be true if you have equilibrated the system using another level 

of theory … 

Best, 

Thomas Kühne

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<zeo_nve.in>

==============================

Thomas D. Kühne

Dynamics of Condensed Matter

Chair of Theoretical Chemistry

University of Paderborn

Warburger Str. 100

D-33098 Paderborn

Germany

thomas...@upb.de

+49/(0)5251/60-5726

[Lucas Lodeiro]

Hello Shamimul Ahsan,

An option to avoid the NVT ensemble is starting from an optimized geometry (well converged) and initializing the NVE MD with 2T temperature, where T is the target temperature. If everything performs well after some picoseconds the MD should be oscilate around T, giving T as the average temperature. This framework works well to me for solid state and isolated molecules.

Regards - Lucas

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[shamimul Ahsan]

Thank you very much Prof. Thomas Kühne and Dr. Lucas Lodeiro for your valuable suggestions. Now my system is running perfectly fine. Thank you very much very once again.

With regards

Shamimul Ahsan

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S.A.M Shamimul Ahsan

Scientific Officer-C

Atomic Mineral Directorate For Exploration & Research

Department of Atomic Energy

Government of India

Nagarbhavi

Bangalore-560072

India