[Pw_forum] Phonon weirdness with matdyn

[Miguel Martínez]

First of all, thanks to Paolo and Eyvaz for their answers.

On Wed, 24 Jun 2009 21:46:05 +0200 Paolo Giannozzi
<giannozz at democritos.it> wrote:
> oops, I guess you are another victim of an ill-conceived change
> I introduced without a careful testing. From file Doc/BUGS
> (recently renamed Doc/release-notes):

The results don't change with quantum-espresso 4.0.5 or the nightly
code tarball from June 23, but I guess Eyvaz is right.



On Wed, 24 Jun 2009 14:46:08 -0700 (PDT) Eyvaz Isaev
<eyvaz_isaev at yahoo.com> wrote:
> Does your sih4.dyn0 contain the macroscopic dielectric constants and
> Born effective charges?

As long as the number is not 0, sih4.dyn* contains both the dielectric
tensor and the Born effective charges, yes.

> If this suggestion is true, then you have LO-TO splitting at the
> Gamma point, and there is no phonon weirdness. Contrary, it reflects
> the real behaviour of the material you studied.

The system is insulating, yes. It doesn't have an enormous gap, but
it's still about 1 eV. I'll take a deeper look at the TO-LO splitting,
because I should have known better... because epsilon_yy is noticeably
larger than epsilon_xx or epsilon_zz.

Thanks everybody again for suggestions and tips,

Miguel


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   UPV/EHU
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