Dear All QE users, i am sorry again, as i havn't corrected the subject title.
(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/ -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110429/2528e0c0/attachment.htm
