BSE and IPA

Deals with issues related to computation of optical spectra in reciprocal space: RPA, TDDFT, local field effects.

Moderators: Davide Sangalli, andrea.ferretti, myrta gruning, andrea marini, Daniele Varsano, Conor Hogan

niloufar
Posts: 34
Joined: Thu Oct 08, 2020 3:53 pm

BSE and IPA

Post by niloufar » Mon Dec 05, 2022 10:17 am

Hello dear developers,
I just did the BSE calculation to get the absorption spectra. The first peak of dielectric function has a huge shift in compare to IPA around 10 ev or more and I'm not sure if it is acceptable or not.
I want to know that this much of shift is possible or not.
Thanks for helping in advance.
Niloufar Dezashibi
Physics and Energy Engineering Department
Amirkabir University of Technology
Tehran, Iran
niloufardezashib@aut.ac.ir
nilo.dezashibi@gmail.com

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Daniele Varsano
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Joined: Tue Mar 17, 2009 2:23 pm
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Re: BSE and IPA

Post by Daniele Varsano » Wed Dec 07, 2022 11:46 am

Dear Niloufar,

not easy to answer with so few details, can you provide more info?, bettere if you post the output and report of your caluculation.
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/

niloufar
Posts: 34
Joined: Thu Oct 08, 2020 3:53 pm

Re: BSE and IPA

Post by niloufar » Fri Dec 09, 2022 7:43 am

Hi again and thanks for your reply.
I attached the files, I should mention that I didn't converge the parameters because I thought it would change the result around 1 ev and not more...
But I faced another problem with bands too, and because they are the same compound and they are related, I attach them here, I'm sorry.

I'm completely confused and really looking forward to your help. My band structure doesn't seem normal and I don't know what the problem is. I converged ecut and Kpoints in scf calculation and I did all convergency parts in yambo before I got the band structure. I attach the files and I would be so over the moon if you help me. thanks in advance.
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Niloufar Dezashibi
Physics and Energy Engineering Department
Amirkabir University of Technology
Tehran, Iran
niloufardezashib@aut.ac.ir
nilo.dezashibi@gmail.com

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Daniele Varsano
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Re: BSE and IPA

Post by Daniele Varsano » Fri Dec 09, 2022 10:11 am

Dear Niloufar,
let's try to go step by step.
1) Band structure, can you repeat the calculation using INTERP_mode= "BOLTZ" and see if you get the expected band structure?
2) The BSE spectrum is indeed very weird, the problem I can see is that the screening has been not read. Note, the report for the screening indicates that the calculation stopped for some reason. Actually, you can either recalculate the screening (static) or use the one you have already calculated it for the GW part (ndb.pp contains also the static part). You can use that screening by generating an input as:

Code: Select all

 yambo -o b -k sex -X p -y d
If you want to recalculate the screening instead (e..g if you want to use different parameters):

Code: Select all

 yambo -o b -k sex -X s -y d
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/

niloufar
Posts: 34
Joined: Thu Oct 08, 2020 3:53 pm

Re: BSE and IPA

Post by niloufar » Fri Dec 09, 2022 10:36 am

Thanks a lot for your time and help, it is so precious. I will try them and post the result.
Niloufar Dezashibi
Physics and Energy Engineering Department
Amirkabir University of Technology
Tehran, Iran
niloufardezashib@aut.ac.ir
nilo.dezashibi@gmail.com

niloufar
Posts: 34
Joined: Thu Oct 08, 2020 3:53 pm

Re: BSE and IPA

Post by niloufar » Sat Dec 10, 2022 12:22 pm

Dear Daniele,
thanks a lot for your help, both problems were resolved and I'm so grateful.
wish you the best
Niloufar Dezashibi
Physics and Energy Engineering Department
Amirkabir University of Technology
Tehran, Iran
niloufardezashib@aut.ac.ir
nilo.dezashibi@gmail.com

niloufar
Posts: 34
Joined: Thu Oct 08, 2020 3:53 pm

Re: BSE and IPA

Post by niloufar » Sun Dec 18, 2022 6:23 pm

Hello dear Daniele,
First I'm thankful again for all your help, and second I have a new problem!
I considered SOC in my QE calculation, but in yambo setup file it identifies my semiconductor as a metal, I think DFT underestimated the gap and it is zero or near zero with soc so this happened. How can I solve this problem? By the way, I didn't do the rest of calculations in yambo because I thought it won't be fixed, can it?
Niloufar Dezashibi
Physics and Energy Engineering Department
Amirkabir University of Technology
Tehran, Iran
niloufardezashib@aut.ac.ir
nilo.dezashibi@gmail.com

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Daniele Varsano
Posts: 3773
Joined: Tue Mar 17, 2009 2:23 pm
Contact:

Re: BSE and IPA

Post by Daniele Varsano » Mon Dec 19, 2022 8:21 am

Dear Niloufar,

you can try to repeat your setup setting ElecTemp=0.0 eV , before you need to remove your ndb* files from the SAVE directory.
if the DFT calculation has a small gap this could solve the problem.
Otherwise, you can ignore the fact the system is metallic and see if a GW calculation opens the gap ignoring the warning about metallic system and Drude not included.
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/

niloufar
Posts: 34
Joined: Thu Oct 08, 2020 3:53 pm

Re: BSE and IPA

Post by niloufar » Mon Dec 19, 2022 9:44 am

OK dear Daniele, I will do that, thanks a million @>-
Niloufar Dezashibi
Physics and Energy Engineering Department
Amirkabir University of Technology
Tehran, Iran
niloufardezashib@aut.ac.ir
nilo.dezashibi@gmail.com

niloufar
Posts: 34
Joined: Thu Oct 08, 2020 3:53 pm

Re: BSE and IPA

Post by niloufar » Wed Jan 04, 2023 3:26 pm

Hello dear Daniele,
thanks a zillion again for all your help.

I did a part of the exciton calculation and got the first bright exciton amplitude, and now I'm willing to show the path on the band structure, I mean show where it happens but I have a question (Sorry if it is stupid). How I can turn the Kpoint coordinate to a.u. values in the band structure axis? like 0.0 0.25 0.25 is what number? :oops:
Niloufar Dezashibi
Physics and Energy Engineering Department
Amirkabir University of Technology
Tehran, Iran
niloufardezashib@aut.ac.ir
nilo.dezashibi@gmail.com

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