[Pw_forum] Questions on phonon calculation in Example02 and 06

[Paolo Giannozzi]

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.
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Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222