Yambo Community Forum

Dear developers,
I performed the BSE calculation by diagonalizing the BS matrix. Where can I find the excitation energies? Should I use some special keywords in the input file to write the excitation energies in the output file explicitly? Thank you very much.

Dear Jianfei Ye

to get information on the excitation energies you should use the ypp (yambo post processing tool, ypp -H for invoking the help)

>ypp -e s

will produce the lists of excitations sorted by the intensity (I) and by the energies (E):
o.exc_E_sorted
o.exc_I_sorted

if you wish you can further analyse the excitation spectrum in terms of eh pairs with

>ypp -e a
for the desired excitation (the numbering as in o.exc_E_sorted) you can obtain (here e.g. for the 5th excitation in the list)
o.exc_amplitude_at_5
o.exc_weights_at_5

where the amplitude for the eigenstate g of the BS Hamiltonian is
A_g(\omega)= \sum_{eh} |<eh|g>|^2 \delta(\omega - E_{eh})

|<eh|g>|^2 is the weight of the eh pair
E_{eh} is energy of the eh pair
the weights and corresponding eh energies are listed in the file o.exc_weights_at_5
from o.exc_amplitude_at_5 you can plot A_g

you can also plot the excitonic wave function

>ypp -e w
>ypp -e w -f

but in this case the diagonalization has to be performed with the (uncommented) key

WRbsWF # [BSS] Write to disk excitonic the FWs

Have fun!

Regards,
m

Dear Dr Myrta Grüning,
thank you for your reply. Your information are very helpful.