3-Body Scattering (3BS) theory of on-site correlation in narrow band materials

We present the results of a recently developed approach where the interplay between the itinerant and localized character of electrons in narrow band materials is described by adding on-site correlation effects to a first principle band calculation: the single particle band states are treated as mean field solutions of a multi-orbital Hubbard Hamiltonian and the many-body term associated to localized e-e interaction is described in a configuration-interaction scheme. The method allows to calculate hole and electron spectral functions which can be directly compared with spectroscopical results.