In general eigenmodes are neither transverse nor longitudinal. Only when the symmetry of the small group of q is sufficiently high eigenmodes can be labeled as T or L. stefano
On Tue, 21 Feb 2006, Konzern wrote: > Dear all, > > There is one question always puzzles me. If my understanding is correct, > for lattice dynamics, the q-point denotes the propagation direction of the > lattice wave, while the eigenvector represents the vibration direction of > a specific atom. Waves whose eigenvectors are perpendicular to the > q-point are transverse waves while parallel are longitudial wave. Moreover, > there should be 2N transverse modes and N longitudial ones. > > However, I checked the results from ph.x, there did not seem to exist > such relations. I am afraid if my understanding was wrong or I have used > the wrong interpretation of the eigenvectors. > > Anyone can help me out? > > Besides, the eigenvectors given by ph.x should be in cartesian coordination, > right? > > Thanks. > > Konzern >
