[Pw_forum] LO-TO splitting in complete phonon dispersion using PWSCF

[Lorenzo Paulatto]

Dear Kondaiah,
I cannot see the picture you have attached (it looks blank here). 
Anyway, the way to tell if a mode is Transverse or Longitudinal is to 
have matdyn save the dynamical matrix for a place next to the Gamma 
point (e.g. q=[0.01 0. 0.], set the input variable fldyn="filename")

An the end of the dynamical matrix file you have the frequencies and the 
atom displacements (3 times number of atoms complex numbers). If the 
displacement for every atom is parallel to the q-point, the mode is 
Longitudinal; if it is orthogonal, the mode is Transverse. In every 
other case it is neither. You can then associated the frequency with the 
label.


HTH


On 20/11/14 15:43, Kondaiah Samudrala wrote:
> Dear Dr. Lorenzo Paulatto
>
>
> Thank you for the conformation.. How can I distinguish the both  modes.. i.e whether LO or TO. Because, in the phonon dispersion plot, I observed  that my GAMMA point having two numbers ( pls see the values Gamma-X and M to Gamma directions...). Here with I am attaching the plot.
>
>
> Please suggest me sir
>
>
> with regards
>
> S. Appalakondaiah
>
> PhD Schloar
>
> University of Hyderabad
>
>
>
>
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-- 
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
phone: +33 (0)1 44275 084 / skype: paulatz
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