Phonon Mode Transformation

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Phonon Mode Transformation

Postby azivkovic » Thu Nov 12, 2015 10:55 pm

Hi,

is it possible that an optical phonon mode can be transformed into a acoustic mode, under any condition, limitation, whatsoever (e.g. pressure induced phase transition)?

Sincerely,
Aleksandar
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Re: Phonon Mode Transformation

Postby mverstra » Sat May 20, 2017 12:13 am

Not sure what you mean. If you dimerize and have a cell doubling, for instance, your acoustic branch at X is folded back to Gamma, and you get an optical branch... Restoring a regular chain of atoms would do the opposite. It depends how you consider your unit cell and whether the displacements are all in phase or not, _and_ whether you mean an acoustic phonon at any q-point or just a Gamma point one...
Matthieu Verstraete
University of Liege, Belgium
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