[Pw_forum] gap in the phonon DOS

[xirainbow]

Dear Reza Ebraahimi:

 I have a question. Does the existence of a gap in the high-energy region of
> the phonon DOS means ionicity of the crystal (splitting of the TO and
> LO-like phonons)? The higher the gap, means the more ionicity?
>
I do not think so.
You can see the "one-dimensional diatomic chain  model" as given in <Dynamic
Theory of Crystal Lattices> written by Max Born and Kun Huang.

____________________________________
Hui Wang
School of physics, Nankai University, Tianjin, China
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