Yambo Community Forum

Dear Yambo developers

I’m trying to reproduce results on Cu bulk at RPA level, published in PRB 64 195125 (A.Marini, G.Onida, R.Del Sole). I’m using a PP with 17 electrons without NLCC and my starting tests seem quite satisfactory. However I have not understood well how Yambo calculates the different contributions to the dielectric function yet.
I would like to know what is the meaning of the two entries in the variable DrudeWXd that Yambo should use to calculate the Drude term of the dielectric function.
According to the short description of Yambo Documentation, it is the Drude Plasmon.
1) Why are there two entries?
2) Why does Yambo need of the Drude plasma frequency? Doesn’t it calculate this frequency solving the equation 17 of the PRB 64 195125?
4) Does Yambo calculate the intraband contribution to the dielectric function by the equation 23 of the PRB 64 195125? Is this equation suitable for metallic surfaces also ?

Thank you in advance for your answers.
Best Regards.

Luca Sementa.
IPCF - CNR
Via G.Moruzzi 1, 56124 Pisa

Luca Sementa wrote:However I have not understood well how Yambo calculates the different contributions to the dielectric function yet.
I would like to know what is the meaning of the two entries in the variable DrudeWXd that Yambo should use to calculate the Drude term of the dielectric function.
According to the short description of Yambo Documentation, it is the Drude Plasmon.
1) Why are there two entries?

The two fields represent the real and imaginary part of the Drude frequency. The imaginary part corresponds to the width of the peak appearing in the EELS.

Luca Sementa wrote: 2) Why does Yambo need of the Drude plasma frequency? Doesn’t it calculate this frequency solving the equation 17 of the PRB 64 195125?

Beacause, as written in the paragraph following Eq.(17) we had to use 16000 random k-points distributed very near the Fermi surface to converge Eq.(17). For this reason Yambo uses an user-defined Drude frequency plugged in a jellium-like analytic expression.

Luca Sementa wrote: 4) Does Yambo calculate the intraband contribution to the dielectric function by the equation 23 of the PRB 64 195125? Is this equation suitable for metallic surfaces also ?

Yes. You can find more information in my PhD thesis, pages 50-55 and pages 137-138.

In case you need more help do not hesitate in posting again here in the forum and I will try top help you.

Andrea

Dear Andrea

Thank you very much for your reply.

Sincerly.

Luca Sementa
IPCF-CNR
Via G.Moruzzi 56124 Pisa

Dear All,
Hoe can i add intraband transition to optical properties?

thanks in advance

Dear m.shahrokhi,
fist of all let me ask you to fill your signature with your affiliation. This is a rule of the forum.

Next, in the following please post you question in the right place of the forum as it can be useful to other users and it's easier to find it. The forum it is divided in subforums divided in topics. I will move your question in the linear response subforum.

About your question, this has been answered here:

viewtopic.php?f=13&t=200&p=1146&hilit=intraband#p1146

Cheers,

Daniele

Dear Daniele
Thank you very much for your quick reply.
Sincerely

Dear Daniele
How do i find the plasma frequency for a metal with yambo?
Should I use the experimental plasma frequency for metals?

Dear Masoud,
yes this is the easiest way.
Fore more details please look at the Andrea Marini answer:
viewtopic.php?f=13&t=200#p1148
to Luca Sementa question.

Where to find the Drude frequency, I do not have an answer but they should be in textbook ad literature.

Cheers,

Daniele

Does the intraband contributions being included in the calculation for a metallic system even if the Drude term in the input file NOT intuduced?
Are the Drude energy and the damping values entered merely a parameter? If not, does the convergence guaranteed?

Dear Burak,
the intraband contribution is *not* taken into account if not specified in the input.
When specified, in enters via the Drude model, so using empirical parameters. Ab-initio inclusion, as you argued, is very hard to converge, you can see an example in the Andrea Marini PhD thesis.

Best,
Daniele