Absorption Calculation using RPA

[ctyrpenou]

Dear Yambo community,

I am new to YAMBO and I performed calculations using IP as starting point then I moved into RPA
then in case of IP I used the attached formula in order to get my absorption curve (e1 is the real
part of dielectric function and e2 is the imaginary one), moving into RPA
tutorial I noticed that in the first lines of the tutorial mentioned that the imaginary part of the macroscopic
dielectric function as a function of frequency is equal to absorption as a function of frequency.
So my question is, should use the attached absorption formula to plot my absorption curve
while I perform calculation under RPA or not ? and how the Im(e(omega)) is related to abs(omega)?

Thank you in advance!

Best regards,
Christos Tyrpenou

[Daniele Varsano]

Dear Christos,

here it is a matter of nomenclature.
The imaginary part of epsilon is related to the absorption, ie its pole are the excitation energies. What you reported is the extinction coefficient, and yes you can apply it also in the RPA approximation.

Best,
Daniele

[claudio]

Dear Christos,

you can find all formula to transform epsilon in reflectivity, absorbance etc.. in this book

Electrodynamics Of Solids -
Dressel, Gruner

that you can download here:

https://www.pi1.uni-stuttgart.de/img/he ... Gruner.pdf

moreover in this repository

https://github.com/yambo-code/yambo-minipy

you can find a script called epsilon/eps_converter.py

that transform epsilon.

best
Claudio

[ctyrpenou]

Dear Daniele and Claudio

Thank you very much for your response and literature sharing.

Best regards
Christos