[Pw_forum] Phonon group velocity in different directions

[Payam Norouzzadeh]

Dear QE users

I have a question about calculation of phonon group velocity:
I know that it is the slope of phonon dispersion curves (w versus k) but
how can I calculate phonon group velocity in different directions of a
crystal like in direction of x,y or z?
Is it possible in QE to calculate them seperately and have vx,vy,vz for
phonons?
I appreciate any useful comment.

Best regards,Payam Norouzzadeh
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