[Pw_forum] applying E-field and results in odd phonon-frequencies, am I allowed to align the frequencies?

[Zohreh Dabiri]

Dear Madam/Sir

I have done some phonon calculations on carbon and silicon using
espresso-5.0.2.

I have done harmonic and anharmonic calculations without any difficulties.

But when I apply various electric fields, phonon frequencies starts from
negative energies.

For instance, phonon frequencies start from -150 meV for Si, while we know
that the material has no instability under electric field, because it’s the
main element in transistors.

Therefore if you wouldn`t mind, I would like to ask am I allowed to shift
the diagrams to zero and make it align to the case that no electric field
was applied?

It would be really nice of you to help me overcome this problem.

Thanks for time and attentions

Best regards

Zohreh dabiri
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