Velocity matrix elements units

[fgoudreault]

Hi,

I'd like to know what are the units of the velocities matrix elements printed out in the IBTEvel_sum.fmt file. Atomic units usually are Hartree x bohr (hbar = 1) however since energies in quantum espresso are typically expressed in Rydbergs, does that mean the velocities are printed out in Rydberg x bohr?

Thanks to anyone clarifying this

Cheers

Felix

[anhhv]

Hi Felix,

The velocity is in Atomic Rydberg Units, "Ry*Bohr/hbar". However, in Atomic Rydberg Units, Bohr = 1 and hbar = 1, thus in order to convert velocity in "IBTEvel_sup.fmt" to SI units, you need to multiply with "factor = Ry*Bohr/hbar", where Ry, Bohr and hbar are all in SI units.

Best,
V.-A.

[fgoudreault]

Hi didn't notice your reply. Thanks a lot for the clarification!