[Pw_forum] Regarding LA-TA modes

[xirainbow]

> Is it possible to get non zero acoustic modes at Gamma point.
    NO.

    Please read books about lattice dynamics, for example "Poulet H,
Mathieu JP. Vibration Spectra and Symmetry of Crystals: Science
Publishers, Inc., 1976."

On Sat, Jul 12, 2014 at 10:38 PM, Kondaiah Samudrala
<konda.physics at gmail.com> wrote:
> Dear all,
>
> I am very much interested in knowing  LA-TA modes and grunessian parameter
> calculations using pwscf.
>
> Is it possible to get non zero acoustic modes at Gamma point. Because, If I
> am applying asr rule at gamma point, the acoustic modes are zero in my case.
> How can we define LA-TA modes ???
>
> Is degenerative modes (Out of First three modes)  are transverse modes???
>
> How to do grunessinn parameter calculations for entire phonon spectrum  in
> PWscf???
>
> Hope positive reply..Thanks in advance
>
> with regards
> S. Appalakondaiah
> PhD student
> University of Hyderabad
>
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-- 
____________________________________
Hui Wang
School of physics, Henan University of Science and Technology, Henan, China