GW vs GGA band gap

Run-time issues concerning Yambo that are not covered in the above forums.

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lamia
Posts: 41
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GW vs GGA band gap

Post by lamia » Sat Jul 11, 2020 9:45 pm

Dear Yambo Developers,

I am running GW calculations and obtaining the band structure. However, when I look at the band structure, I see that the band gap (1 eV) of GW is equal to the band gap (1 eV) of DFT-GGA . How is this possible?

Best,
Taouil Lamia
University of Mohammed V
Faculty of science - Rabat
Morocco

Palummo Maurizia
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Re: GW vs GGA band gap

Post by Palummo Maurizia » Sun Jul 12, 2020 4:32 pm

Dear Taouil

without further detail it is impossible to help you.
Please provide at least the input and report files of your GW and ypp post-processing runs.

Best
Maurizia
Dipartimento di Fisica
Universita' 'Tor Vergata'
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tel.++39-06-72594894
fax.++39-06-2023507
http://www.fisica.uniroma2.it/~cmtheo-group/

ETSF European Theoretical Spectroscopy Facility www.etsf.eu

lamia
Posts: 41
Joined: Mon Dec 05, 2016 5:09 pm

Re: GW vs GGA band gap

Post by lamia » Mon Jul 13, 2020 4:33 pm

Dear Maurizia,
Thank you for your reply.
You'll find the input of GW and ypp post-processing runs.

Best,
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Taouil Lamia
University of Mohammed V
Faculty of science - Rabat
Morocco

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Daniele Varsano
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Re: GW vs GGA band gap

Post by Daniele Varsano » Tue Jul 14, 2020 8:04 am

Dear Taouil,
in order to include GW correction in the band structure, you need to provide the QP database in the input file:
GfnQPdb = " E < ./SAVE/ndb.QP"
if the QP database is in the SAVE directory, otherwise you need to indicate the path where the database is.

Best,
Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/

lamia
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Joined: Mon Dec 05, 2016 5:09 pm

Re: GW vs GGA band gap

Post by lamia » Wed Jul 15, 2020 7:43 pm

Dear Daniele,

Should I add GfnQPdb = " E < ./SAVE/ndb.QP" in yambo.in input file or just in ypp.in or both ? I've tried to add it in ypp.in but I still get same band structure.

best,

Lamia
Taouil Lamia
University of Mohammed V
Faculty of science - Rabat
Morocco

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Daniele Varsano
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Re: GW vs GGA band gap

Post by Daniele Varsano » Thu Jul 16, 2020 6:57 am

Dear Lamia,
the QP correction in G has to be added in the ypp.in. If the bands are the same it means that the QP corrections are not read correctly. To understand what went wrong can you post the report and output?

Best,
Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/

lamia
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Re: GW vs GGA band gap

Post by lamia » Thu Jul 16, 2020 11:53 am

Dear Daniele,

You'll find the report and output files in the attachments.

Best,

Lamia
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Last edited by lamia on Thu Jul 16, 2020 12:13 pm, edited 1 time in total.
Taouil Lamia
University of Mohammed V
Faculty of science - Rabat
Morocco

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Daniele Varsano
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Re: GW vs GGA band gap

Post by Daniele Varsano » Thu Jul 16, 2020 12:11 pm

Dear Taouil Lamia,
from the report it seems the QP corrections are read correctly.
Can you try to repeat the calculation by commenting the BANDS_path variable, and using
GfnQPdb= "E < ./SAVE/ndb.QP"
instead of:
GfnQPdb= "E < SAVE/ndb.QP"
if the correction is not applied please post also the output file.

Best,

Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/

lamia
Posts: 41
Joined: Mon Dec 05, 2016 5:09 pm

Re: GW vs GGA band gap

Post by lamia » Thu Jul 16, 2020 12:27 pm

Dear Daniele,

I've tried with your last suggestion .

PS: I should get an indirect band gap with 2.43 eV
best,
lamia
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Taouil Lamia
University of Mohammed V
Faculty of science - Rabat
Morocco

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Daniele Varsano
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Re: GW vs GGA band gap

Post by Daniele Varsano » Thu Jul 16, 2020 1:36 pm

Dear Taouil Lamia,
I was meaning the bands outputs you calculated with and w/o the GfnQPdb input variable.

Best,

Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/

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