optical absorption plot

[Daniele Varsano]

Dear Reza,

please note that in your calculations, you are not considering any QP corrections, nor GW calculated energies neither scissor operator. Is this intentional?

If you want, you can share the report/output files of the two calculations to have a look at what they do differs besides the time-ordering.

Best,
Daniele

[Reza_Reza]

Dear Daniele,

I redo some calculations to verify the results.
I have attached the needed documents.

Best,

Reza

[Daniele Varsano]

Dear Reza,

the calculations indicated you have a negative excitation energies. In the positive region, the resonant and retarded response differs as they should, as the restarted is forced to be antisymmetric with respect to the zero energy origin. Besides that they also slightly differ as the screening is calculated with a different number of bands.

It is not attached the report of the BSE-GW curve, I suppose it is a calculation where you have applied a GW correction to the energy with a retarded time ordering.

For a better analysis, as you have solved the BSE with a full diagonalization you can inspect the eigenvalues using ypp:

Code: Select all

ypp -e s b 1 -J Optic

Best,

Daniele

[Reza_Reza]

Dear Daniele,

I have attached the GW report as well. I also inspected the eigenvalue of "retarded" time ordering. The first and strongest exciton has negative energy, as indicated in optical absorption.

Best,

Reza

[Daniele Varsano]

Dear Reza,

ok, all seems consistent. You have the resonant and retarded calculation, indicating a negative excitation energy (instability). The plot of the absorption are different indeed because of the time-ordering.

Best,

Daniele