[Pw_forum] question about q-point and eigenvector from ph.x

[Konzern]

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
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