[Pw_forum] matdyn file output

[Denny Jackson]

Hello,

I am having trouble understanding the output from ph.x in the matdyn file.
I am looking at Barium Titanate in the cubic phase, but with broken symmetry
and then relaxed.
I'm trying to compare the linear response frequencies from ph.x to frozen
phonon frequencies.  From what I understand, the diagonalized dynamical
matrix should give displacements of each atom.  So in the output:

omega( 4) =       3.763989 [THz] =     125.553988 [cm-1]
 (  0.097362  0.000000 -0.116603  0.000000 -0.288197  0.000000 )
 ( -0.066349  0.000000  0.077204  0.000000  0.200853  0.000000 )
 ( -0.169282  0.000000  0.204883  0.000000  0.421687  0.000000 )
 ( -0.159112  0.000000  0.218980  0.000000  0.474827  0.000000 )
 ( -0.184271  0.000000  0.191581  0.000000  0.474679  0.000000 )

each column gives the real and imaginary components of the displacements in
cartesian coordinates.  I could not find what units these values have, first
of all.  I assume they are unitless and are a fraction of the lattice
parameter.
Also, each column should add up to zero to preserve symmetry, should it
not?  For higher frequencies in this calculation the columns do indeed add
up to zero, but for lower frequencies (and negative frequencies) this is not
the case.  Does this indicate a problem with my pw calculation or something
else?

Is there a resource for good documentation on the matdyn file I have
overlooked?

Thanks for helping,

Dennis Jackson
Oregon State University
denny.jackson at gmail.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.democritos.it/pipermail/pw_forum/attachments/20090826/de025b05/attachment.htm