[Pw_forum] Phonon freqencies

[Sonu Kumar]

To know TO and LO modes, you have to
specify the direction in k-space along which you want to see the splitting.

Also, see the post
http://qe-forge.org/pipermail/pw_forum/2014-November/105682.html

bests,
sonu


On Thu, Aug 24, 2017 at 2:58 PM, Uttam Paliwal <uttamphy at gmail.com> wrote:

> Dear QE users
> I am computing phonon frequencies for BeS. I am attaching here the output
> file part
>
>
>
>      q = (    0.000000000   0.000000000   0.000000000 )
>
>  ***********************************************************
> ***************
>      freq (    1) =       0.105756 [THz] =       3.527650 [cm-1]
>      freq (    2) =       0.105756 [THz] =       3.527650 [cm-1]
>      freq (    3) =       0.105756 [THz] =       3.527650 [cm-1]
>      freq (    4) =      16.460235 [THz] =     549.054328 [cm-1]
>      freq (    5) =      16.460235 [THz] =     549.054328 [cm-1]
>      freq (    6) =      16.460235 [THz] =     549.054328 [cm-1]
>  ***********************************************************
> ***************
>
>      Mode symmetry, T_d (-43m)  point group:
>
>      freq (  1 -  3) =          3.5  [cm-1]   --> T_2  G_15 P_4   I+R
>      freq (  4 -  6) =        549.1  [cm-1]   --> T_2  G_15 P_4   I+R
>
>
> ************************************************************
> ******************
> these are TO (Transverse Optical) or LO (Longitudinal Optical), how to
> know. please suggest
>
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