Model dielectric matrices for quasiparticle self-energy calculations

A computationally simple model for the full static dielectric matrices is proposed for use in self-energy calculations to obtain quasiparticle energies and band gaps. The screening hole around an added electron at a given point in the crystal is approximated by the screening response of a homogeneous medium determined by the local density. The resulting approximation to the screening potential includes the crucial part of the local fields. When used with the previously developed self-energy approach, quasiparticle energies and band gaps in good agreement with experimental results are obtained for diamond, Si, and Ge.