Fig. 1: Lowest-order diagrams for the contribution of the electron–phonon interaction to the zero-point renormalization of the gap ZPRg.
From: Predominance of non-adiabatic effects in zero-point renormalization of the electronic band gap
a Fan diagram, with two first-order screened electron–phonon vertices; b Debye-Waller diagram, with one second-order screened electron–phonon interaction vertex.
