[Pw_forum] phonon eigenvector units

[David Miller]

Hello,

I have performed a phonon calculation using ph.x. During the scf calculation (prior to using ph.x), the ATOMIC_POSITIONS is in Bohr units. I am also using ibrav = 0 and an orthorhombic crystal system. After ph.x, I have used dynmat.x to apply asymmetric sum rule and  get the new phonon eigenvalues and eigenvectors. The output of dynmat.x has the following format: 


     omega(12) =       1.305968 [THz] =      43.562397 [cm-1]
 ( -0.052340   0.000000    -0.021008   0.000000     0.002346   0.000000   )
 ( -0.003841   0.000000    -0.009204   0.000000     0.053835   0.000000   )
 (  0.014655   0.000000    -0.015822   0.000000     0.085998   0.000000   )
 ( -0.013791   0.000000    -0.035434   0.000000     0.066956   0.000000   )

While the units of omega is evident, the unit of eigenvectors is not clear. I wonder what is the unit of eigenvectors ?

The atomic position have the following units:
ATOMIC_POSITIONS { alat | bohr | crystal | angstrom }

Do the phonon eigenvectors have the same units as atomic positions or they have one particular unit always ? If it is one particular unit then what it is ? I noticed that the dynamical matrix is written in cartesian axes (I assume it means  in the units of alat). 

Thanks,

David
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