[QE-users] Determining anisotropic dielectric function with turbo_eels.x and turbo_espectrum.x

[Anibal Bezerra]

Dear Quantum Espresso users and developers,

I've followed the discussion in a previous set of messages sent to this
forum about using  turbo_eels.x and turbo_espctrum.x to determine the
dielectric function. Taking a look at the documentation, I've seen that the
programs return a "single" component of the *chi* and *eps* functions,
depending on the transferred momentum vector.

Is it possible to check for dielectric function anisotropic response by
using the different transferred momentum vectors? I mean:
-> x response Q=(qx,0,0)
-> y response Q=(0,qy,0)
-> z response Q=(0,0,qz)

Taking a look at the hands-on presentation " Time-Dependent Density
Functional Perturbation Theory:" by Iurii Timrov, he compared turboDavidson
and turboLanczos. In particular, he showed that at turboLanczos we can
choose polarization by the variable ipol = 1,2,3, and 4.  Example 01 of
TDDFPT packages does Lanczos calculation using ipol=4, but the results (eps
and chi) have only imaginary and real parts of a single component. I would
expect different responses for each direction (x,y,z, since ipol=4), is it
right?

Tanks in advance!

Anibal Bezerra
Federal University of Alfenas
Alfenas-MG
Brazil
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