[QE-users] LO-TO splitting for Phonon DOS

[Paolo Giannozzi]

On Tue, Sep 22, 2020 at 9:30 AM Jakob Kraus <
jakob.kraus at physik.tu-freiberg.de> wrote:

>
> judging from the matdyn.f90 source file, it seems possible to include
> LO-TO splitting in the calculation of the phonon DOS.
>
> However, I have not figured out the correct way to enter the direction
> of the q vector in the matdyn input file.
>

it is explained in the header of matdyn.f90, from line 128:

!  If q = 0, the direction qhat (q=>0) for the non-analytic part
!  is extracted from the sequence of q-points as follows:
!     qhat = q(n) - q(n-1)  or   qhat = q(n) - q(n+1)
!  depending on which one is available and nonzero.
!  For low-symmetry crystals, specify twice q = 0 in the list
!  if you want to have q = 0 results for two different directions

Paolo

 Chttps://
gitlab.com/QEF/q-e/-/commit/52d65b3cdbcc578c5e637082f5b82375471a242f

>
> Could you provide with an example of a matdyn input file that
> incorporates LO-TO splitting in the direction of, let's say, q=(1,0,0)?
>
>
> Moreover, I've noticed that, even though I've set epsil = .false. for
> the phonon calculation for a metal, the ph.x code seems to calculate a
> (wrong) dielectric tensor if ldisp = .true.
>
> Does ldisp somehow override epsil in this case?
>
>
> Thank you very much in advance for your time and effort.
>
> It is very much appreciated.
>
>
> Best regards,
>
>
> Jakob Kraus
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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