[Wien] mBJ calculation for semimetallic system

[Rubel, Oleg]

Hi Fabien.

The paper (http://dx.doi.org/10.1021/acs.jpca.7b02882) does not mention SOC. I assume it is done without SOC? In SnTe SOC is important. It opens the gap, if I recall it correctly, which would also make sense for a topological insulator. SOC vs no-SOC could explain the difference between my results (PBE 0.24 eV and TB-mBJ 0.13 eV) and your results (0.07 and 0.15 eV, respectively).

Best regards
Oleg

________________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of Tran, Fabien <fabien.tran at tuwien.ac.at>
Sent: Friday, July 17, 2020 16:55
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] mBJ calculation for semimetallic system

Hi,

Thanks for your comments. For which structure of SnTe did you get these gaps? In
http://dx.doi.org/10.1021/acs.jpca.7b02882
the PBE and mBJ gaps of SnTe (SG 225) are 0.07 and 0.15 eV, respectively?

FT

________________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of Rubel, Oleg <rubelo at mcmaster.ca>
Sent: Friday, July 17, 2020 10:43 PM
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] mBJ calculation for semimetallic system

Hi Myung-Chul,

in addition to Fabien's comments, I had a very positive experience with TB-mBJ also for semimetals. For instance, (HgCd)Te alloy has a negative band gap on the HgTe-reach side. TB-mBJ predicts the negative gap correctly (https://doi.org/10.1103/PhysRevB.90.115202), while PBE makes it too negative. With TB-mBJ we were able to get correct zero-gap (HgCd)Te composition.

Regarding topological materials: SnTe is an interesting material system. It has the experimental band gap of 0.18 eV. PBE overestimates (!) the band gap and yields 0.24 eV, while TB-mBJ gives a smaller (!) gap of 0.13 eV. I would definitely trust more  TB-mBJ in this case.

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: http://olegrubel.mcmaster

________________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of Tran, Fabien <fabien.tran at tuwien.ac.at>
Sent: Thursday, July 16, 2020 03:36
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] mBJ calculation for semimetallic system

Hi,

mBJ was proposed for the calculation of band gaps, which are more realistic than with LDA/PBE
for nonmagnetic semiconductors and insulators, as well as antiferromagnetic systems.

Concerning semimetals and topological insulators, I would recommend to search for results obtained with
mBJ for systems which are similar to the ones you want to study.

F. Tran



From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of Aaron Jung <kangbugy at gmail.com>
Sent: Thursday, July 16, 2020 8:15 AM
To: wien at zeus.theochem.tuwien.ac.at
Subject: [Wien] mBJ calculation for semimetallic system

Dear users and developers,

Hello,

I performed the mBJ calculation in a semimetallic system, but it has a tiny gap already.
As considering SOC, the system becomes a semiconducting state.

I have two questions.
First, to investigate the Z2 indices on bulk system, I conduct the eigen parity for each TRIM points.
In the mBJ calculation, the eigen parity is reliable? That is, can I accept the result of parity eigen value from the irrep calculation?

Second,
For LDA+mBJ calculation,
Can I use the mBJ approach for semimatallic and nonmagnetic system?

Thank you,
Myung-Chul.

=============================================================
Myung-Chul Jung
Postdoctoral Researcher

Electronic Structure Theory Group (E6-2, 4310)

Department of Physics, Korea Advanced Institute of Science and Technology

291 Daehak-ro, Yuseong-gu, 34141, Korea
=============================================================
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