[Pw_forum] Pw_forum Digest, Vol 46, Issue 89

[sonu kumar]

Dear All QE users,

> (2) only cubic crystals has LO and TO braches.
>

crystals ( having considerable values of macroscopic dielectric constant [ i
suppose
epsilon infinity] and born effective charges, as pointed  out by Prof. Eyvaz
Isaev) with low symmetry can, also, have LO-TO splitting. But this can be
 different in different symmetry directions, so one has to search all
symmetry directions for this splitting.

For cubic crystals splitting is equal in all directions.

with regards,
-- 
Sonu Kumar

Phd Student
Physics Department
Indian Institute of Technology
Delhi-110016, India
web:-http://www.iitd.ac.in/
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