Bulk water MD, PM6-FM and full PBC

[Ivan Gladich]

Dear CP2K users

 I would like to perform a bulk water simulation using PM6-FM semiempirical method. My goal is to have a flavor of a chemical reaction between organics in bulk water and, afterward, refine it at DFT-MD level.

I am a newbie on semiempirical methods. I used PM6-FM because it seems appropriate for liquid system

(https://groups.google.com/g/cp2k/c/BjBMWoq0doE/m/QADgmxMhAQAJ )

 I started inspired by some examples in CP2k github. I made two attempts, but both give me unreasonable results

 1)    A water cluster in vacuum at 300 K. After a short while, the system "kind of freezes" and nothing is moving

 2)    A bulk water box in PBC: after a short while all hydrogens detach from the water oxygen

 Thus, Is it possible to perform semiempirical  (PM6-FM or other) MD in full PBC? Does anyone have a successful input to share or point that  I can use as a starting point?

 I attach my inputs if someone is interested to check.

The initial configuration was taken from an equilibrated water box of 1.9 nm X 1.9nm X 1.9nm equilibrated at  classical MD at 1 bar and 300 K

 Thank you very much for any possible help or suggestion

Best regards

Ivan

[Ruel]

Hi Ivan, did you manage to get PM6-FM method to work with PBC? I have also the same problem of broken O..H bonds.

Ruel

[Thomas Kühne]

Dear Ivan and Ruel, 

please find a sample input that we have used for a related system attached - maybe it’s helpful. 

Best, 

Thomas

[Ivan Gladich]

Dear Thomas

Thank you very much

I am going to test it

Best and thank you again

Ivan

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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

thomas...@upb.de

+49/(0)5251/60-5726

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