[Pw_forum] Regarding LA_TA modes

[Lorenzo Paulatto]

On 07/30/2014 03:20 PM, Kondaiah Samudrala wrote:
> Dear all,
>
> I'm wondering if anybody knows how to identified LA-TA modes along high symmetry directions.
>

If the displacement pattern of the atoms and the q-point are parallel, 
the mode is longitudinal; if they are orthogonal the mode is transverse. 
When a special q point has a symmetry equivalent copy that is orthogonal 
to itself, TA and LA will be degenerate, I'm not sure this is the only 
case when this can happen.

bests

-- 
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
+33 (0)1 44 275 084 / skype: paulatz
http://www.impmc.upmc.fr/~paulatto/
23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20140730/6d4a6e01/attachment.html>