We pubblised a new paper^{1} on the optical properties of Cu-chalcogenide photovoltaic absorbers. In this manuscript we calculate the optical response of the less studied, but promising, Cu_{2}ZnGe(S,Se)_{4} compounds, opening the way to predictive calculations of still unknown materials by means of self-consistent GW plus Bethe-Salpeter equations.

Moreover in this paper we solved the problem of the dipoles calculation starting from self-consistent GW or in general from any non-local self-energy/functional. We used the dipoles definition of Blount^{2}

and finite difference approach to define dipoles without calculate any commutator with the non-local part of the Hamiltonian.

**References:**

- Optical properties of Cu-chalcogenide photovoltaic absorbers from self-consistent GW and the Bethe-Salpeter equation

Phys. Rev. B**91**, 075134 (2015)

Sabine Körbel, David Kammerlander, Rafael Sarmiento-Pérez, Claudio Attaccalite, Miguel A. L. Marques, and Silvana Botti

- Formalisms of band theory

E.I. Blount, Solid State Physics,**13**,*page 305-73.**New York,**Academic Press,*(*1962*)