absorption spectra using slepc and diagonalization

Deals with issues related to computation of optical spectra, solving the Bethe-Salpeter equation.

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Priyanka
Posts: 7
Joined: Thu May 11, 2023 5:27 pm

absorption spectra using slepc and diagonalization

Post by Priyanka » Fri Jan 19, 2024 12:42 pm

Dear Experts

I attempted to compute absorption spectra using slepc and diagonalization methods, however the results of both calculations are entirely different. I followed the tutorial but still was unable to figure out what is wrong in my case. Please assist me in solving this problem. The required files are attached here.

Thanks in advance,
With warm regards
Priyanka
University of Modena and Reggio Emilia
Italy.
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Daniele Varsano
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Re: absorption spectra using slepc and diagonalization

Post by Daniele Varsano » Fri Jan 19, 2024 1:01 pm

Dear Priyanka,

the spectrum calculated with slepc includes only the poles and residues evaluated at the difference of the complete diagonalization, where all the eigenvalues are included. I suspect that something can go wrong in the slepc algorithm where too many eigenvector are considered.

For this reason, slepc is meant for the analysis of the first excitations and not for the computation of the entire sepctrum.

What I suggest you is to compare directly the eigenvalues that can be inspected by using the ypp utility (ypp -e s )

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/

Priyanka
Posts: 7
Joined: Thu May 11, 2023 5:27 pm

Re: absorption spectra using slepc and diagonalization

Post by Priyanka » Fri Jan 19, 2024 3:40 pm

Dear Daniele

Thank you for your inputs. I will try this.

Thanks in advance,
With warm regards
Priyanka
University of Modena and Reggio Emilia
Italy.

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