Yambo Community Forum

Hello dear developers,

I just started to run yambo code and as a first step I got the optical absorption of Cs2PbBr3 with ( yambo -F yambo.in_IP -o c ) But when I plot the .eps files, I got the same numbers in all axises (x,y,z). I mean, when you plot them together, you can't see any differences. Is there a problem? How can I fix that?

Thank you in advance

Dear Niloufar,

can you attach your input and output files (attachments bottom bellow)?
when uploading file you need to rename it with a supported format e.g. (.zip or .txt)

Many thanks,
Daniele

Hi Daniele,
Thanks a lot for helping. I attached the input file and the outputs.

sincerely,
Niloufar

Dear Niloufar,
the spectra are very similar, but not identical.
It seems your system is homogeneous along that direction.
You can check the symmetries in your report or qe output, if they are recognised.

Best,
Daniele

Dear Daniele,

I will check that in my qe files.

thank you very much,
Niloufar

Hi,

I have computed the optical absorption for a low-dimensional system (1D) with a small bandgap (DFT = 0.15 eV, GW = 0.31 eV). Since the bandgap is very small, a negative formation energy for the exciton is expected. However, the optical absorption spectra appear unusual when using BSEmod = "retarded".

I have attached the optical absorption data and a detailed report. I want to know if there might be an issue with the calculation.

All necessary parameters were carefully converged.
For the figure, I plotted "o-Optic.alpha_q1_diago_bse" using u 1:2 w l linewidth 2 t 'Retarded', as it is a low-dimensional system.

Best regards,

Reza

Dear Reza,

the retarted response function seems correct for a negative excitation energy, as it is enforced to be antisymmetric with respect to the zero energy.
What it is strange is the difference you obtain from resonant and retarted at positive energies, are you sure they do differs only for the time-ordering, is it possibile that what you indicate as resonant it is an IP calculation?

Best,
Daniele

Dear Daniele,

Thanks for the response.
Is it possible that what you indicate as resonant it is an IP calculation? No, it is not. For both cases, I used Chimod = "HARTREE". The only flag I changed was BSEmod = "retarded"

Best,
Reza

Dear Reza,

Chimod="Hartree" indicates that you are calculating the screening matrix at Hartree level (RPA).
The BSE kernel instead is selected by the BSKmod variable.

Best,
Daniele

Dear Daniele,

Thanks, It is BSKmod= "SEX" for both calculations.
I attached the input file.

Best,
Reza