questions about the results of BSE calculations?

Deals with issues related to computation of optical spectra, in RPA (-o c) or by solving the Bethe-Salpeter equation (-o b). Includes local field effects, excitons, etc.

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Dean
Posts: 44
Joined: Thu Oct 10, 2019 7:03 am

questions about the results of BSE calculations?

Post by Dean » Thu Sep 10, 2020 8:36 am

Dear developers,
1. After doing BSE calculations with Diago solver, I want to analyze the exciton oscillator strenght and amplitude and got the file o-2D.exc_weights_at_1, which shows :
# Electron-Hole pairs that contributes to Excitonic State 1 more than 5%
#
# K-point [iku] Weight
# 0.26667 0.46667 0.00000 0.09283
# 0.333333 0.500000 0.000000 1.000000
#
# Band_V Band_C K ibz Symm. Weight Energy
#
21.00000 22.00000 27.00000 2.00000 0.90921 2.06548
21.00000 22.00000 27.00000 1.00000 0.90919 2.06548
My question is why it show two same kpoints (ibz: 27) contributing to this Excitonic State? but two different k-points in iku Points coordinates?
2. After doing BSE calculations with Inversion solver, the file o-2D-.eps_q1_inv_bse shows 7 columns. What does each column stand for?
With regards,
Thanks.
Dr. Yimin Ding
Soochow University, China.

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Daniele Varsano
Posts: 2605
Joined: Tue Mar 17, 2009 2:23 pm
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Re: questions about the results of BSE calculations?

Post by Daniele Varsano » Thu Sep 10, 2020 9:11 am

Dear Yimin,
My question is why it show two same kpoints (ibz: 27) contributing to this Excitonic State?
These are not the *same* k point in the BZ, but two k points related by symmetry (4th column)!
The matrix relating the two k points is listed in the report file where the symmetries are indexed (here 1 is the identity, the index 2 is listed in the report).
but two different k-points in iku Points coordinates?
This is a different list, as in the K-point analysis all the v-> c transitions our a given k points are summed up.
o-2D-.eps_q1_inv_bse shows 7 columns. What does each column stand for?
# E/ev[1] EPS-Im[2] EPS-Re[3] EPSo-Im[4] EPSo-Re[5] EPS`-Im[6] EPS`-Re[7]
energy, imaging/real part of eps , imag/real part of non interacting eps , imag/real part of eps for the iteration before convergence

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/

Dean
Posts: 44
Joined: Thu Oct 10, 2019 7:03 am

Re: questions about the results of BSE calculations?

Post by Dean » Fri Sep 11, 2020 2:02 am

Dear Daniele,
Thanks very much.
Dr. Yimin Ding
Soochow University, China.

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