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-chemical ab initio calculations on appropriate molecules. In distinction from previous cluster simulations, we consider a set of comparably small molecules rather than a large cluster, which allows us to use extended one-particle basis sets. We then extract local matrix elements from these calculations and use them to set up an incremental expansion for the bulk band structure. The question how to extend our method to the determination of the conduction-band structure and the band gap is discussed.