Yambo Community Forum

Hi everyone,

I am currently engaged in a research project investigating the optical properties of monolayer 2D materials. In particular, I am focused on computing the static macroscopic dielectric constant (epsil2D(q)) as a function of the 2D q vector, as outlined in Equation (6) of the reference [Falco et al., PRB 88, 245309 (2013)].

For this calculation, I plan to utilize the Random Phase Approximation (RPA) and truncated Coulomb interaction. I am aware that Yambo facilitates the use of truncated Coulomb interaction through parameters like RIM_W and RandGvecW.

My specific question is whether it is feasible to obtain epsil2D(q) by injecting these parameters directly into the Yambo input file for an RPA calculation (yambo -o c -k hartree -V par -RPA.in). If this approach is not suitable, I would greatly appreciate any guidance or suggestions you may have on how to proceed with this particular computation.

Thank you in advance for your time and assistance.

Best regards,
Smiri Adlen
Postdoctoral Researcher
Mathematics for Advanced Materials Open Innovation Laboratory (MathAM-OIL)
National Institute of Advanced Industrial Science and Technology (AIST)
c/o Advanced Institute for Materials Research
Tohoku University
2-1-1, Katahira, Aoba-ku, Sendai,
Miyagi 980-8577, Japan

Dear Smiri,

the RIM_W technique is meant to integrate the screened potential and not for its evaluation on a specific k point.
The technique is explained in:
A. Guandalini et al: https://www.nature.com/articles/s41524-023-00989-7


What you can do is to evaluate the eps_2D by the calculation of the polarizability (e.g. in RPA) which is an output of Yambo.
See e.g. Eq. 6 in Rasmussen et al. PHYSICAL REVIEW B 94, 155406 (2016)

Hope it helps,

Daniele

Dear Daniele Varsano,

I appreciate your prompt response and guidance.

Following your suggestion on evaluating eps_2D through the calculation of polarizability, I am curious if there exists a tutorial demonstrating the computation of alpha_2D using the W-average method. Currently, I am using Yambo 5.1, and in the output of the RPA calculation, I observe only eps and not the polarizability alpha. While I am aware of the relationship between the static dielectric constant and alpha_2D as presented by Cudazzo et al., I am interested in understanding if there is a direct method for computing alpha.

Additionally, I've encountered Equation 6 in the work by Rasmussen et al. (PHYSICAL REVIEW B 94, 155406, 2016), and I acknowledge that it primarily captures the physics in the long-wave limit. However, I am curious about the possibility of extracting the dielectric function matrix eps_GG'(q) corresponding to the truncated Coulomb interaction (v) in a manner that satisfies the screening potential (W): WGG'(q)=eps_GG'(q)^-1 v(q+G')?

Your insights and any available resources or tutorials on these topics would be immensely beneficial.

Thank you once again for your assistance.

Best regards,
Adlen

Dear Adlen,
please sign your posts, you can do once for all by filling the signature in your user profile.
The polarizability alpha is in the output by default when a coulomb cutoff is used. If you do not have o.alpha* file, it means that for some reason the coulomb cutoff potential has been neglected, and I would need the input/report file to understand what happened.

I am curious about the possibility of extracting the dielectric function matrix eps_GG'(q) corresponding to the truncated Coulomb interaction (v) in a manner that satisfies the screening potential (W): WGG'(q)=eps_GG'(q)^-1 v(q+G')?

This can be done using the yambo-py utility.
You can install and follow some tutorials. If you have particular question, you can ask in the yambo-py subforum:
https://www.yambo-code.eu/wiki/index.ph ... in_Yambopy
https://github.com/yambo-code/yambopy

Best,

Daniele

Dear Daniel,

Thank you very much for your help

In fact, in my previous calculations, i did not use a Coulomb cutoff. Therefore, according to your explanation, I did not get alpha in the output because of this reason.
In my new calculation (attached files), I used Coulomb cutoff parameters in the input by using yambo -r option. However, only the LOG folder and the report file appear in my output directory? No alpha files?

Best,

Dear Adlen,
at the end of the report file, there is the mirror of the input file actually read by Yambo and I can see:
By default, Yambo reads "yambo.in" file, if you rename it you need to redirect by using the -F option e.g.:
> yambo -F yambo_rpa.in

If no input file is present, Yambo just perform a setup calculation.

Best,
Daniele