PROJECTS

Development of local electron correlation methods for periodic systems

PRINCIPAL INVESTIGATOR

PD Dr. Martin Schütz Universität Stuttgart Theoretische Chemie Pfaffenwaldring 55 D-70569 Stuttgart (+49)711/685-4409 (+49)711/685-4442 schuetz@theochem.uni-stuttgart.de

PROJECT RESEARCH ASSISTANT

ABSTRACT

In recent years, based on the local correlation ansatz of Pulay and Saebo, On electron correlation methods for molecules including highly correlated Coupled Cluster models were developed in the Stuttgart group. These methods exploit the fact that dynamic electron correlation effects between remote parts of a molecule (manifesting as dispersive interactions in intermolecular perturbation theory) decay with a R-6 with respect to the distance R between these fragments much more quickly than the Coulomb interactions that are treated already at the Hartree-Fock level. In order exploit this "short sighted-ness" of dynamic correlation local molecular orbitals are introduced to span the occupied and virtual spaces (specified by the underlying Hartree-Fock calculation). Dramatic savings in the computational cost could be achieved without significant loss in accuracy. In the present project, related local methods for periodic systems will be developed. Wannier functions, generated within a Hartree-Fock approach, serve as one-electron functions to span the occupied space. In the spirit of the Pulay/Saebo ansatz, non-orthogonal projected AOs (PAOs) will be used to span the virtual space, obtained from the atomic orbitals by projection onto the virtual space. As in the case of isolated molecules, it should then be possible to construct a priori excitation domains and a hierarchy of electron pairs, essential ingredients to arrive at. On algorithms to treat electron correlation. Target systems are polymers, nucleotide base stacks, crystalline insulators, and semiconductors.