Abstract
A local-orbital based ab initio approach to calculate correlation effects on quasi particle energies in insulating solids is presented. The use of localized Wannier-type Hartree Fock orbitals allows to efficiently devide correlation effects into classes of strong, medium or small weight. Subsequently the strongly contributing correlations are obtained from a Green's function calculated by exact diagonalization, while the rest is taken into account by a perturbative treatment. With this method the band structure of LiH is calculated and reasonable agreement with experiment is found.
