[Wien] Born effective charge calculation

[Wien2k User]

Dear Dr.  Oleg Rubel,
it is exactly like our case, we have obtained a very small band-gap with
GGA (close to zero), but relatively a large value with mBJ.
Thanks for you and for Prof. L. Marks

Le lun. 7 sept. 2020 à 17:23, Laurence Marks <laurence.marks at gmail.com> a
écrit :

> 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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