Yambo Community Forum

Hi

I am doing the GW and BSE calculations for a 2D metallic system. Following the tutorial for 2D hBN (http://www.yambo-code.org/wiki/index.ph ... al_systems), I got the following warning:

[WARNING][K+QP] Metallic system
[WARNING] The system is a metal but Drude term not included.
[WARNING]Fractional e/h occupations but resonant only mode selected in input.

I guess this means that I need do some extra calculations before starting running the GW and BSE calculations demonstrated in the tutorial. Could you please help me with this? How can I include the Drude term? Thanks

Dear Siyu Chen,

yambo is warning you that your system is metallic.
You can include the Drude tail in an empirical way in the BSE calculation by using the DrudeWBS.
This is empirical so you need to provide in input the frequency of the Drude plasmon and its width, something you can hopefully find in literature for your system. Otherwise, you can also discard it but you will not have the metallic behaviour in the spectrum.
Note that anyway the metallic screening is not accounted in the q=0 term in the dielectric matrix, this means that probably you will need many k points to converge your sepctrum. Finally, you can consider to go beyond the resonant approximation in the BSE kernel considering a causal response or adding the coupling terms.

PS: we are working in this period to enhance the capability of Yambo to treat metallic systems, hopefully, it will be ready soon.

Best,
Daniele