[Wien] Born effective charge calculation

[Laurence Marks]

The evidence I could find is that with LDA/PBE/PBEsol/mBJ Born charges are
slightly too large compared to experiment. Hybrid methods give slightly
(10%) smaller values which seem to be closer to experiment. A caveat is
that I could not find extensive, good experimental data.

N.B., of course a metal does not have a Born charge...

---
Prof Laurence Marks
"Research is to see what everyone else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu

On Mon, Sep 7, 2020, 10:41 Rubel, Oleg <rubelo at mcmaster.ca> wrote:

> To add to the discussion, here is a tutorial "Born effective charge of
> GaN" from the last WIEN2k workshop (
> https://urldefense.com/v3/__http://susi.theochem.tuwien.ac.at/events/ws2019/Exercises_19-tot.pdf__;!!Dq0X2DkFhyF93HkjWTBQKhk!GdNcHpBDzmc0bKkfTPuHupsF84fQAHYEE4SpKCD6n0q9kD52LHuFkiYuzaf5sysilMJE0g$
> ). In this case LDA performs very well. One can try to do TBmBJ to see a
> difference.
>
> Some systems with a small Eg (for example InN) have Eg = 0 at LDA/GGA
> level, which created a problem for Berry phase calculations that need a
> gap. In this case TBmBJ (or DFT+U) would be your best option.
>
> I hope it will help
> Oleg
>
> --
> Oleg Rubel (PhD, PEng)
> Department of Materials Science and Engineering
> McMaster University
> JHE 359, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada
> Email: rubelo at mcmaster.ca
> Tel: +1-905-525-9140, ext. 24094
> Web:
> https://urldefense.com/v3/__http://olegrubel.mcmaster__;!!Dq0X2DkFhyF93HkjWTBQKhk!GdNcHpBDzmc0bKkfTPuHupsF84fQAHYEE4SpKCD6n0q9kD52LHuFkiYuzaf5sys_YsgAaQ$
>
> ________________________________________
> From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of
> Laurence Marks <laurence.marks at gmail.com>
> Sent: Saturday, September 5, 2020 22:39
> To: A Mailing list for WIEN2k users
> Subject: Re: [Wien] Born effective charge calculation
>
> From what I have found and my tests, either -eece or +U are better as
> GGA's overestimate. MBJ does not appear to be better. However, values are
> often not that well measured experimentally.
>
> ---
> Prof Laurence Marks
> "Research is to see what everyone else has seen, and to think what nobody
> else has thought", Albert Szent-Gyorgi
> http://www.numis.northwestern.edu<http://www.numis.northwestern.edu>
>
> On Sat, Sep 5, 2020, 19:09 Wien2k User <wien2k.user at gmail.com<mailto:
> wien2k.user at gmail.com>> wrote:
> Dear Wien2k users,
>
> Is it more precise to use mBJ for the calculation of born effective charge
> or gga is sufficient? (in a case where there is no comparison values)
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