How to calculate optical properties

[amirmehdi89]

Dear Yamboers,

First of all, I apologize if this post is a bit lengthy. I am very new to Yambo and I am interested in calculating the optical properties of a system consisting of silicon, oxygen, and sometimes hydrogen. Going through the tutorials and literature for Yambo, I have learned a little bit how to do the type of calculation I am looking for. However, I still have not been able to understand some aspects of Yambo in depth. I will start with the following questions:

1. I have my DFT database from QE. In order to do optics, do I have to do BSE or GW+BSE or …? Whichever the answer is, would you provide the command for it?

2. Let’s say it is GW+BSE that I have to do. Should the convergence tests be done based on the parameters of this specific type of the calculations? Or I have to update the database first by doing for example static screening first or something like that (for example some other type of calculation)?

Long story short, I think I am a little lost in terms of which type of the calculations I have to be looking for. Any help would be thoroughly appreciated. Thank you

[Daniele Varsano]

Dear Amir,

1. I have my DFT database from QE. In order to do optics, do I have to do BSE or GW+BSE or …? Whichever the answer is, would you provide the command for it?

It depends of the level of approximation you want to calculate the absorption spectrum: GW/BSE, TDDFT, RPA. Each of them has different parameters to be converged and the tutorial are meant to learn how to generate the input files and which are the key parameters to care about.

Should the convergence tests be done based on the parameters of this specific type of the calculations?

Yes, the convergence are always system dependent

Or I have to update the database first by doing, for example, static screening first or something like that (for example some other type of calculation)?

If you do BSE you need to calculate the static screening, you can do it in a separate run or in the same run selecting different runlevels together.

I think I am a little lost in terms of which type of the calculations I have to be looking for.

I cannot really help on that, what kind of calcaltion you need to look for it depends on your research, it is something you need to discuss with your supervisor/collaborators.
I strongly suggest you to take your time to go through the theory and do the step by step tutorials.

Best,
Daniele