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

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Daniele Varsano
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Re: BSE and IPA

Post by Daniele Varsano » Thu Jan 05, 2023 3:19 pm

Dear Niloufar,
you can convert the kpoints from rlu (reciprocal lattice units) to Cartesian coordinates.
You can wither do it by yourself reading the lattice parameter from the setup report, or print the list of k points using the ypp utility.

Code: Select all

ypp -k k 
setting in ypp.in:
cooOut= "cc"
and inserting the list of k points you want to convert in:
%GWKpts namelist.

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 » Thu Jan 05, 2023 4:16 pm

Thank you a lot 🌷🌷🌷
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 » Tue Jan 17, 2023 8:02 pm

Hi dear Daniele,
I have a question about the strength and amplitude of excitons. I've seen the formula and I can understand it mathematically, but can you help me with the more precise meaning of them and how are they different?

Thank you in advance for your help @>-
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
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Re: BSE and IPA

Post by Daniele Varsano » Wed Jan 18, 2023 5:23 pm

Dear Niloufar,

the amplitude provides you a way to see which independent particle transitions the most participate to the formation of the exciton, and you have in output the energy of these transitions weighted according to the solution of the BSE |Acv!^2:
https://www.yambo-code.eu/wiki/index.ph ... _amplitude

The strength is also related to the weight A_cv but takes into account the dipole moment of each transition, so it tells you if an exciton is bright or dark and how much is intense the absorption of the light at that energy.

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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