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ENERGY DRIFT

Started by Daqiang, April 07, 2018, 03:08:37 PM

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Daqiang

Hi Dr Dubbeldam:
   I used the RASPA2.0.3 to simulate the isotherm of acetylene. However, when the pressure is higher than about 1500 Pa, I got a warning in the output file.
   
Simulation finished,  1 warnings
WARNING: ENERGY DRIFT (INTERNAL CONSISTENCY ERROR IN THE CODE), THE SIMULATION RESULTS ARE WRONG!!

How can I resolve the warning? Adding the NumberOfCycles?

Thanks,

Daqiang

David Dubbeldam

For any error, always retry with the latest version (which is RASPA 2.0.30).

Daqiang

Thank David. Using the latest version, I have resolve the issue.

Somananda Sanyal

Dear Dr. Dubbeldam,

    I am getting the same error with the latest version of RASPA, i.e. 2.0.35.
How to resolve the warning and if I may know too why is it occurring?

Thanks.
Somananda

David Dubbeldam

This can possibly occur when not all potentials are well-defined. An example is when the hydrogens do NOT have a Lennard-Jones potential, but the connecting atom has a VDW radius that encompasses the hydrogen (or it should). But if the VDW radius is too small, then at high density the atoms will start to overlap leading to numerical problems.

kokojiang

Dear Dr. Dubbeldam,

    I am getting the same error too. Like what you explained, the error happened as the number of adsorbates increased. When the number of adsorbates is low, it works well. But when the number of adsorbates is large, like 2500, the error appeared. In the forcefield I use, hydrogens did have no lennard-jones potential. How can I solve this warning? Should I change the forcefield or just run a larger simulation cycle?

Thank you!.
Jiang

David Dubbeldam

I would modify the force field. One of the options is to put a hard-sphere potential around the hydrogen to shield it from overlap.

neumannrf

Dear Dr. Dubbeldam,

We are having a similar problem with C2H2 and would like to try your suggestion, but we could not find in the manual how to set up a hard-sphere potential on the Hydrogen. What are the keyword and parameters?