[QE-users] Query about vibrational energy

[Pooja Vyas]

Dear users,

I want to compute the vibrational energy of a structure (B2 phase of CaO)
which is unstable and has negative phonon frequency but positive density of
states. The QHA module of QE does not compute vibrational energy and
entropy for such structures. Is it correct to use the standard equation of
vibrational energy (See Eq. 6 in
https://sci-hub.ee/10.1016/j.matchemphys.2011.05.014)  for such negative
frequencies? If not, what is the other way to compute it?

Thanks.
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