Diabatic electronic states from many-body perturbation theory

Abstract

We apply the so-called diabatization method by Baer (1975 Chem. Phys. Lett. 35 112) to describe photo-excited electronic states. The diabatization is a unitary transformation which, applied to the adiabatic eigenstates of the quantum Hamiltonian, allows for treating the non-adiabatic effects correctly. These effects are all those which appear in the Born–Oppenheimer approximation as the areas of avoided crossings in the potential energy surfaces. The diabatization is placed in the context of the scheme of ab initio many-body perturbation theory (density functional theory with the GW method with Bethe–Salpeter equation (DFT-GW-BSE)) calculation of materials.