Just to add a (hopefully, clarifying) comment. Hermitean matrix: eignevalues are real, eigenvectors are in in general complex Real symmetric matrix: eigenvalues are real (because the matrix is Hermitean as well). The eigenvectors *CAN* be chose to be real. This does not imply that they *MUST* be chosen so.
You may want to rethink to the previous replies in the light of this remark. Also, I am almost certain that this very question has been already discussed in this forum. You may want to check the archive. Take care Stefano B. On Nov 19, 2007, at 12:03 PM, Paolo Giannozzi wrote: > > On Nov 19, 2007, at 12:31 , Ion Errea wrote: > >> Does anyonone which are the reasons why you can get imaginary >> displacements for phonon eigenmodes? > > at q=0 both the dynamical matrix and its eigenvectors are real, > but for a general q, the dynamical matrix is complex hermitian > and its eigenvectors are in general complex > > Paolo > --- > Paolo Giannozzi, Dept of Physics, University of Udine > via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum --- Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype) Please, if possible, don't send me MS Word or PowerPoint attachments Why? See: http://www.gnu.org/philosophy/no-word-attachments.html -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20071119/600792c9/attachment-0001.htm
