potential files of qbox

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luke419
Posts: 14
Joined: Tue Feb 27, 2024 2:50 am

potential files of qbox

Post by luke419 »

Hello,

Many thanks for your answers, Francois.
There two types of potentials, ONCV_PBE-1.2 and HSCV_PBE-1.0, for qbox and I'd like to know differences between them.
Would you let me know to what applications they are more suitable and/or needed essenitially, respectively?

It seems that ONCV needs more computational cost than HSCV.
For spin-orbit coupling calculation, would ONCV be better than HSCV?
Can I use HSCV not only for example cases but also for liquid water AIMD with a rather high accuracy for hydrogen-bond and/or IR spectrum analysis?

Best regards,

Young
fgygi
Site Admin
Posts: 162
Joined: Tue Jun 17, 2008 7:03 pm

Re: potential files of qbox

Post by fgygi »

Hello Young,

Both the HSCV and ONCV potentials should be adequate for water simulations. The PBE400 dataset http://www.quantum-simulation.org/refer ... /index.htm and the SCAN330 dataset http://www.quantum-simulation.org/refer ... /index.htm were generated using the HSCV potentials. The ONCV potentials have additional non-local projectors, which should make them more accurate. This incurs an additional computational cost. However, the HSCV potentials require a higher plane wave cutoff (85 Ry) than the ONCV (which is apparently good with 65 Ry). I do not have accurate comparisons of timings of these potentials in the same conditions.

Regarding spin-orbit interactions, note that Qbox does not currently compute such interactions. If you mean "spin-polarized", this is supported by setting the variable nspin to 2.

If you are interested in MD simulations for IR spectra, HSCV may be ok, but you should use an 85 Ry cutoff. I would still recommend using ONCV in spite of a possible addiional cost.

Note also that if you want to compute the stress tensor, the plane wave cutoff should be increased. Please refer to the PBE400 and SCAN330 papers for details (see links above).

Francois
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