DeepMD-ZBL Shifting Energy by energy of atom in vacuum

[JRVHouston628]

Hello,

I'm trying to use the DeepMD-ZBL methodology referenced here: https://arxiv.org/pdf/1904.00360.pdf for Si irradiation simulations using the use_srtab command. I am using QuantumEspresso to train the model. Do I need to ensure the energy documented in the tabulated file converges to the energy of a Si in a vacuum as calculated by Quantum Espresso at large distances? That is, does the ZBL potential need to be shifted down?

[wanghan-iapcm]

No. The tab potential only switches on when the neighbors are very close to an atom. It has no effect on the asymptotic behavior at large distance.

[wanghan-iapcm]

I would prefer shifting the DFT energy zero point, but not shifting the ZBL potential. @JRVHouston628 have you tried this option?

[JRVHouston628]

I haven't tried this yet, but I think it's worth a try. Let me spend some time on this and I'll get back to everyone.

[JRVHouston628]

DeepMD_ZBL.docx

Hi all,
I still have not tried shifting the DFT zero point energy as of yes, but I wanted to attach a document summarizing my findings that I mentioned. I show the potential energy of an Si-Si dimer for two cases:

The first case is using a DeepMD+ZBL potential where the tabulated potential was shifted down to match the calculated zero-point energy. The potential energy curve appears smooth and well behaved, however when I hit the surface with a Si atom (with a kinetic energy of 100 eV), the entire simulation cell explodes.

The second case is using a DeepMD+ZBL potential where the tabulated potential was NOT shifted down to match the calculated zero-point energy. The potential energy curve shows some odd behavior (as expected) in the region where smoothing occurs (between 1 and 1.6 angstroms). However despite this apparent oddity in the dimer potential energy, the simulation cell remains stable when hit with a Si atom with kinetic energy of 100 eV.

I would have thought the first case would be more well behaved given how smooth the dimer potential energy looks, however the opposite is true. Can someone explain why this is happening? I was under the impression that only the forces are important, but it appears whether or not you shift your ZBL potential significantly affects results.

[wanghan-iapcm]

We have supported shifting the tabulated potential, please check #2670

[JRVHouston628]

Thanks I'll give this a try soon! I appreciate the help!