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 & Universit? Paris 6 +33 (0)1 44 275 084 / skype: paulatz http://www.impmc.upmc.fr/~paulatto/ 23-24/4?16 Bo?te courrier 115, 4 place Jussieu 75252 Paris C?dex 05 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20140730/6d4a6e01/attachment.html
