LO-TO splitting is a general feature of polar materials. It means that the frequency of the (3N-3) optical modes at gamma depends on the direction you are approaching from. for any given direction the number of optical modes is always 3N-3 but they are in general different in different directions. In the particular case of elemental semiconductors with cubic symmetry the 3 optical modes are split in 2 TO and 1 LO modes whose eigenvalues do not depends on the direction BUT their eigenvectors DO depend on the direction ... In general both the eigenvalues and the eigenvectors depend on the direction
stefano Reza Ebraahimi wrote: > Hello everyone > i have a question about the LO-TO splitting. Imagine an insulator or > semiconducting bulk material that has no degenerate phonon mode at Gamma > point (no "E" or "T" species after diagonalizing the Dynamical matrix). > Should this bulk exhibit LO-TO splitting? Cause in this case, the # of the > optical modes becomes more than 3N-3, right? > Thank You in Advance > > R. Ebraahimi > Graduate Student- Tehran University > > > > > > ------------------------------------------------------------------------ > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
