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dielectric function don't match literature
Posted: Wed Apr 12, 2023 11:05 pm
by Peace
Dear all,
I'm a beginner in Yambo and I want to plot the optical properties but i'm facing an issue.
I generated the files bellow:
Code: Select all
r_optics_dipoles_chi yambo.in r_setup o.eel_q1_ip SAVE o.eps_q1_ip
I know that to plot the imaginary and real part of dielectric function we use o.eps_q1_ip file . The problem is that I found very big values in the y-axis [-20,140 ] as in the attached picture, that don't match the literature [-4,8] . Can you help me figure out where the problem is coming from, please?
Re: dielectric function don't match litteerature
Posted: Thu Apr 13, 2023 10:59 am
by myrta gruning
Hello,
It is important to make sure that the values that are chosen for the numerical parameters (number of k-points and selected bands) are at convergence, meaning that you have to study the convergence of the spectrum with these parameters and choose the parameters such that the spectrum is not changing (within some tolerance) when further increasing the parameters.
It would be helpful if you attach the report of the calculation. From what I can see, I believe you would need to increase the number of k-points.
Finally, note as well, that the intensity of the spectra depends on the value for the damping (DmRngeXd) though usually the default value should be reasonable and you can leave it as it is for the moment.
Re: dielectric function don't match literature
Posted: Thu Apr 13, 2023 3:41 pm
by Peace
Dear Myrta,
For the k-points I used gamma. Isn't that ok?
What is DmRngeXd because I can notice that there is a difference in intensity between my calculations and literature?
Re: dielectric function don't match literature
Posted: Mon Apr 17, 2023 7:35 am
by Daniele Varsano
Dear Salma,
DmRngeXd is the damping range used to calculated the spectrum (Lorentzian peaks). It affects the intensity as the oscillator strength is the are beneath your peaks.
A smaller damping gives you higher intensity and narrower peaks. Providing two values the damping increases linearly between the two values in the range of energies set in EnRnge. If you want a constant damping you need to set the same value for the two entries.
Best,
Daniele
Re: dielectric function don't match literature
Posted: Tue Apr 18, 2023 10:39 am
by Peace
Dear Daniele,
Can you show me how to change those variables through an example please? By the way I'm using Yambo with Quantum ESPRESSO
Re: dielectric function don't match literature
Posted: Mon Apr 24, 2023 8:49 am
by Daniele Varsano
Dear Salma,
For the k-points I used gamma. Isn't that ok?
It depends, if your system is an isolate molecule it is OK, otherwise if it is a bulk or 2D system etc. you need to sample the Brillouin zone.
About the damping:
% DmRngeXd
0.10000 | 0.10000 | eV # [Xd] Damping range
%
In this way, you introduce a damping of 0.1eV along all the energy range of the spectrum. You can reduce or enlarge by changing the two values e.g. (0.05 | 0.05| or 0.2 | 0.2|)
Best,
Daniele