Yambo Community Forum

Dear YAMBO user,

I want to calculate the optical properties of graphene using quantum espresso + YAMBO (for GW correction). For this I have done scf and nscf calculation in quantum espresso and used p2y from Yambo bin to make the database of YAMBO. Then I calculate optical properties using yambo using the command yambo -o c -k h -p p . Now I am getting a problem regarding the plotting of optical absorption. In my graphene.save file their are 72 folder for k points, and I have found 72 file for epsilon [o.eps_qi_inv_rpa_dyson (i=1......72)]. Now my question is
1) How can I plot the epsilon from all 72 files? Is their any script or post prossesing tool available for this?
2) Or can I add all this epsion from different 72 files to get total epsilon?

Here I have attached the input and output file . I am waiting for kind suggestion. Thanking you in advance.

Sincerely
Barnali
Ph.D scholar, Department of physics,
Assam University,
India

Dear Barnali,


1) GW is an approximation for the quasi-particle energy and not for optical absorption, in order to calculate absorption in many body framework you need to perform a Bethe-Salpter calculation.

2) yambo -o c -k h -p p: you are calculating optics in linear response "yambo -c -k hartree" at RPA level, and moreover you are calculating dynamical screening in Plasmon Pole approximation. So, no QP energies, but just producing databases for the PP approximation.

3) You have many files, because you are computing the linear response for all the q vectors. The macroscopic dielectrix function (optics) is given for the q->0 limit and it is the first file: o.eps_q1_inv_rpa_dyson
If you are not interested at the dispersion in q (interesting for eels) and you are interested in optics only, you can consider to do the calculation setting: this will avoid the calculation of the response at finite q points.

Hope it helps, but I strongly suggest you before starting to use Yambo, to take your time to study some basis of the theory, reading some literature or reviews on Many Body Perturbation Theory and optical properties, e.g. REV MOD PHYS, 74 (2): 601-659 APR 2002.
Have look at the documentation in the yambo website (you can find there several compendium of the theory), familiarize with the inputs looking to the tutorials, and read carefully the reports and output files in order to understand what you are calculating.

Please, next time, try to post your question in the correct place of the forum, as in general, threads can be found ad could be useful to other users. Your question doe not fit the topic (Importing core database/pw).

Best,
Daniele