Many-electron bands in transition metal compounds

A new method is presented for generating correlated many-electron bands for localized excited states, hole states and added-electron states in extended systems with strong electron correlation effects. The method allows for a rigorous treatment of the local electronic response that accompanies the excitation process. The energy bands are calculated with an ab initio many-electron non-orthogonal tight-binding approach. The corresponding wave functions consist of optimized linear combinations of local many-electron basis functions. The many-electron basis is obtained from multiconfiguration wave functions for large embedded clusters. Each local state is expressed in terms of its own optimized orbitals set. To demonstrate the method we investigate the dependence of the energies of the lowest added-electron states in the perovskite CaMnO3. These states are important for understanding the interplay of conduction and magnetism in doped CaMnO3.