VALENCE-BAND STRUCTURE OF GROUP-IV SEMICONDUCTORS BY MEANS OF LOCAL INCREMENTS

We present a method to determine the correlated valence-band structure of covalent semiconductors that uses information from quantum-chemica l ab initio calculations on appropriate molecules. In distinction from previous cluster simulations, we consider a set of comparably small m olecules rather than a large cluster, which allows us to use extended one-particle basis sets. We then extract local matrix elements from th ese calculations and use them to set up an incremental expansion for t he bulk band structure. The question how to extend our method to the d etermination of the conduction-band structure and the band gap is disc ussed.