[Pw_forum] ?propagation direction of LO-TO splitting for dynmat.in file phonon calculation

[Pietro Delugas]

Dear Wei

LO modes should be computed along the direction of the dipoles of 
InfraRed (IR)  active modes.

Anatase is tetragonal, mode dipoles can be either parallel to the axial 
direction or perpendicular to that, in this latter case the relative 
mode has to be  doubly degenerate, and thus any direction perpendicular 
to the axis is OK.

The only important thing is the direction, the module of the q vector 
has no influence on the result.

greetings Pietro


On 25/12/2016 16:24, Wei Li wrote:
> Dear Stefano de Gironcoli,
>
> Thanks for your words.
>
> Regarding the anatase bulk tio2, which direction should I choose to 
> propagate? And also how large the q(i) is?
>
> thanks, Merry Christmas!
>
> Wei
>
> -- 
> *Wei Li*
> PhD student
> State Key Lab of Theoretical & Computational Chemistry
> Institute of Theoretical Chemistry
> Jilin University
> Changchun, 130023
> P.R. China
> Email: liwei0099 at gmail.com <mailto:liwei0099 at gmail.com>
>
>
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