creating a mixed van der Waals damping scheme

[Andrey Poletayev]

Hello! 

This may be a dumb question coming from a beginner user. I am looking to use CP2K for training ML potentials for water. I found this recent work on chemRxiv combing through functionals (although they used VASP) : https://chemrxiv.org/engage/chemrxiv/article-details/66616c4e21291e5d1d301165 

They argue that the best behavior of simulated water is achieved with about 50% of Becke-Johnson damping with revPBE0+D3. There are two options - either compute every frame twice (zero damping and B-J) and average, or make up a halfway damping. Is it possible / straightforward to create such a halfway damping? 

Thank you,

-Andrey

[Jürg Hutter]

Hi

I don't know what "50% of Becke-Johnson damping with revPBE0+D3" really means, but you
can provide the input parameters to the D3(BJ) method with

FORCE_EVAL / DFT / XC / VDW_POTENTIAL / PAIR_POTENTIAL

D3BJ_SCALING (s6,a1,s8,a2)

regards
JH

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Subject: [CP2K:20526] creating a mixed van der Waals damping scheme

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[Andrey Poletayev]

Just to clarify the jargon in my orginal post: the chemRxiv argues that water ML potential trained with the revPBE0 functional and van der Waals damping set to average between zero and Becke-Johnson is the most accurate. 

Thank you for the answer, it sounds like I could attempt to halve the relevant coefficients first. 

Andrey

[Andrey Poletayev]

Poking around the documentation, it seems I should be able to repeat the PAIR_POTENTIAL section twice, one for the DFTD3 zero damping, and the second for DFTD3(BJ), each with SCALING of 0.5, to average the two dispersions, each with its appropriate parameters set by D3_SCALING and D3BJ_SCALING respectively.

Does this seem reasonable / is SCALING just a linear strength coefficient? 

The default of 0 on SCALING is a bit confusing because I would think the default SCALING would be 1. 

Andrey