On Oct 15, 2009, at 2:16 , vtmtrinh at caltech.edu wrote: > I compared the 2 results from the 2 methods, I saw that both ways gave > the same phonon frequencies, but the displacement vectors are totally > different.
no they aren't. Displacement vectors for non-degenerate modes (number 3 and 6) are the same (within numerical accuracy). For degenerate modes, you get different linear combinations (because of the way matrix diagonalization works), but the subspace spanned by the two sets of degenerate eigenvectors is the same (I haven't verified, but I am sure it is: plase verify) P. --- Paolo Giannozzi, Dept of Physics, University of Udine via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
