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.