[Wien] contradictory band gap in case.scf and band.agr

[Fecher, Gerhard]

Why don‘t you just tell your structure ?

Ciao
Gerhard

DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
"I think the problem, to be quite honest with you,
is that you have never actually known what the question is."

====================================
Dr. Gerhard H. Fecher
Institut of Physics
Johannes Gutenberg - University
55099 Mainz
________________________________________
Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Dr. K. C. Bhamu [kcbhamu85 at gmail.com]
Gesendet: Samstag, 10. September 2022 13:20
An: A Mailing list for WIEN2k users
Betreff: Re: [Wien] contradictory band gap in case.scf and band.agr

Dear Gavin

Thanks for your reply.
I have checked with both the approaches and I am having same problem in both the cases.

On Sat, Sep 10, 2022, 4:24 PM Gavin Abo <gabo13279 at gmail.com<mailto:gabo13279 at gmail.com>> wrote:

I have probably overlooked in your conversion when you mentioned whether you were using a shifted or non-shifted k-mesh; If you happened to have used a shifted k-mesh in your perovskites calculation, then you might try the calculation again with a non-shifted k-mesh during "x kgen":

https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg15445.html
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg19427.html
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg15445.html

Kind Regards,

Gavin
WIEN2k user

On 9/10/2022 4:20 AM, Dr. K. C. Bhamu wrote:
Thanks Prof. Marks for your suggestions.

My system is non-sp and non-SO type.

I didn't do any mistake with k-path as Its a cubic system and its brillouin zone is very simple.

I do agree with the k-mesh as with very fine mesh narrow band gap systems may show metallic character.
In one of my case it is happening.


But in a separate case where I didn't change the k-mesh after SCF for band structure calculation, the band structure should show the same band gap as I am getting with the grep command. No?

Thanks
Bhamu

On Sat, Sep 10, 2022, 3:11 PM Laurence Marks <laurence.marks at gmail.com<mailto:laurence.marks at gmail.com>> wrote:
I can think this can occur in numerous ways, all a minor mistake:

1. You forgot to include -orb when you did the bands.
2. You had too small a k-mesh for the scf, the fine one for the bands shows a metal.
3. Your grep showed just the "up" spin, not both.
4. You did not fully converge.
5. You forgot -so in the band.
6. You have a mistake in your k-mesh for the bands.
7. Something else similar.

Just my guesses, I suggest you check carefully. Number 7 is most likely.

--
Professor Laurence Marks
Department of Materials Science and Engineering, Northwestern University
www.numis.northwestern.edu<http://www.numis.northwestern.edu>
"Research is to see what everybody else has seen, and to think what nobody else has thought" Albert Szent-Györgyi

On Fri, Sep 9, 2022, 10:45 PM Dr. K. C. Bhamu <kcbhamu85 at gmail.com<mailto:kcbhamu85 at gmail.com>> wrote:
Dear Users

Greetings,

I am trying to compute the band structure of some ABX3 perovskites systems with Wien2k_19.2 compiled with intel compilers.
When I grep the band gap from case.scf, I am getting some values (~0.7eV) while when I plot the band structure, the VBM is significantly crossing the Fermi level and the gap between CBM and VBM is much lesser than the one I grepped from case.scf file.
In some case, VBM and VBM are overlapping while case.scf file is showing a clear band gap.

I have updated Fermi energy in case.insp files.

I never faced such an issue in the past.

I am wondering if you would like to help me out.

Regards
Bhamu

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