screening and electron coupling strength

[luca.montana]

Dear Developers,

since the electron-phonon coupling strength increases by decreasing electron screening ( by starting from different (non-)hybrid DFT functionals),
does it mean at the same time that the zero point energy correction to the electronic band gap decreases, too ?

in summary : does the increase of the electron-phonon coupling strength means decrease of the zero point correction to the electronic gap ?

Is the above statement correct from physical point of view ?

Best wishes
LUCA

[giustino]

Hi Luca,

Generally speaking and very (very) roughly the correction to the band gap scales with the square modulus of the electron-phonon matrix element, the matrix element scales with the inverse of the dielectric function, and the dielectric function scales with the inverse of the square of the band gap. As a result one can expect that a functional yielding a wider gap will also give a larger zero-point renormalization of that gap.
This manuscript by Antonius et al discusses this change from LDA to GW: http://link.aps.org/doi/10.1103/PhysRevLett.112.215501
I collected some examples of recent work on this aspect in Sec. XII of http://arxiv.org/abs/1603.06965

FG

[luca.montana]

Dear Feliciano,

many thanks for your answer.

Best wishes
LUCA