<div dir="ltr">Dear Dr.
Oleg Rubel,<div>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.<br></div><div>Thanks for you and for Prof. L. Marks</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Le lun. 7 sept. 2020 à 17:23, Laurence Marks <<a href="mailto:laurence.marks@gmail.com" target="_blank">laurence.marks@gmail.com</a>> a écrit :<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="auto"><div>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.</div><div dir="auto"><br></div><div dir="auto">N.B., of course a metal does not have a Born charge...<br><br><div dir="auto">---<br>Prof Laurence Marks<br>"Research is to see what everyone else has seen, and to think what nobody else has thought", Albert Szent-Gyorgi<br><a href="http://www.numis.northwestern.edu" target="_blank">www.numis.northwestern.edu</a></div><br><div class="gmail_quote" dir="auto"><div dir="ltr" class="gmail_attr">On Mon, Sep 7, 2020, 10:41 Rubel, Oleg <<a href="mailto:rubelo@mcmaster.ca" target="_blank">rubelo@mcmaster.ca</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">To add to the discussion, here is a tutorial "Born effective charge of GaN" from the last WIEN2k workshop (<a href="https://urldefense.com/v3/__http://susi.theochem.tuwien.ac.at/events/ws2019/Exercises_19-tot.pdf__;!!Dq0X2DkFhyF93HkjWTBQKhk!GdNcHpBDzmc0bKkfTPuHupsF84fQAHYEE4SpKCD6n0q9kD52LHuFkiYuzaf5sysilMJE0g$" rel="noreferrer noreferrer" target="_blank">https://urldefense.com/v3/__http://susi.theochem.tuwien.ac.at/events/ws2019/Exercises_19-tot.pdf__;!!Dq0X2DkFhyF93HkjWTBQKhk!GdNcHpBDzmc0bKkfTPuHupsF84fQAHYEE4SpKCD6n0q9kD52LHuFkiYuzaf5sysilMJE0g$</a> ). In this case LDA performs very well. One can try to do TBmBJ to see a difference.<br>
<br>
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.<br>
<br>
I hope it will help<br>
Oleg<br>
<br>
--<br>
Oleg Rubel (PhD, PEng)<br>
Department of Materials Science and Engineering<br>
McMaster University<br>
JHE 359, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada<br>
Email: <a href="mailto:rubelo@mcmaster.ca" rel="noreferrer" target="_blank">rubelo@mcmaster.ca</a><br>
Tel: +1-905-525-9140, ext. 24094<br>
Web: <a href="https://urldefense.com/v3/__http://olegrubel.mcmaster__;!!Dq0X2DkFhyF93HkjWTBQKhk!GdNcHpBDzmc0bKkfTPuHupsF84fQAHYEE4SpKCD6n0q9kD52LHuFkiYuzaf5sys_YsgAaQ$" rel="noreferrer noreferrer" target="_blank">https://urldefense.com/v3/__http://olegrubel.mcmaster__;!!Dq0X2DkFhyF93HkjWTBQKhk!GdNcHpBDzmc0bKkfTPuHupsF84fQAHYEE4SpKCD6n0q9kD52LHuFkiYuzaf5sys_YsgAaQ$</a> <br>
<br>
________________________________________<br>
From: Wien <<a href="mailto:wien-bounces@zeus.theochem.tuwien.ac.at" rel="noreferrer" target="_blank">wien-bounces@zeus.theochem.tuwien.ac.at</a>> on behalf of Laurence Marks <<a href="mailto:laurence.marks@gmail.com" rel="noreferrer" target="_blank">laurence.marks@gmail.com</a>><br>
Sent: Saturday, September 5, 2020 22:39<br>
To: A Mailing list for WIEN2k users<br>
Subject: Re: [Wien] Born effective charge calculation<br>
<br>
>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.<br>
<br>
---<br>
Prof Laurence Marks<br>
"Research is to see what everyone else has seen, and to think what nobody else has thought", Albert Szent-Gyorgi<br>
<a href="http://www.numis.northwestern.edu" rel="noreferrer noreferrer" target="_blank">http://www.numis.northwestern.edu</a><<a href="http://www.numis.northwestern.edu" rel="noreferrer noreferrer" target="_blank">http://www.numis.northwestern.edu</a>><br>
<br>
On Sat, Sep 5, 2020, 19:09 Wien2k User <<a href="mailto:wien2k.user@gmail.com" rel="noreferrer" target="_blank">wien2k.user@gmail.com</a><mailto:<a href="mailto:wien2k.user@gmail.com" rel="noreferrer" target="_blank">wien2k.user@gmail.com</a>>> wrote:<br>
Dear Wien2k users,<br>
<br>
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)<br>
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