[QE-users] Occupation calculation - epsilon.x code

[Anibal Bezerra]

Dear QE users and developers,

The epsilon.x manual (in the PP/DOC folder) shows the possibility of
calculating occupations using the key "occ" within the epsilon.x. It is
emphasized to be a good tool to analyze convergency against the broadening
parameter and the k points sampling. However, the "occ" calculation is not
implemented (at least in the version I'm using - 6.4). Such a calculation
was implemented with other packages?

If not, is there a way of verifying the convergence other than explicitly
changing the broadening and k points sampling?

I'm working with an AuAl alloy, trying to evaluate the dielectric function.
Using epsilon.x I've got anisotropic behavior that I was not expecting for.
Working with pure systems (Au and Al) I concluded that reducing conv_thr
increases the epsilon.x output precision, returning the isotropic behavior
of the dielectric function. Therefore, to the alloy (with 12 atoms in the
cell), I increased both the conv_thr (1e-13) and k points (14 14 14). I
still got the anisotropy. Should I go further (calculations with my actual
computing power are becoming very time and memory consuming)?

Thanks in advance!!

Anibal Bezerra
The Federal University of Alfenas
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