PROJECTS

Development of local electron correlation methods for periodic systems

PRINCIPAL INVESTIGATOR

Prof. Dr. Martin Schütz Universität Regensburg Physikalische und Theoretische Chemie Universitätsstraße 31 D-93040 Regensburg (+49) 941-943-4717 (+49) 941-943-4719 martin.schuetz@chemie.uni-regensburg.de

PROJECT RESEARCH ASSISTANT

ABSTRACT

In recent years, On electron correlation methods for molecules including highly correlated Coupled Cluster models were developed. These methods use the fact that dynamic electron correlation is a local (short-range) effect, which can be exploited, provided that a local orbital basis is used to construct the Fock space. Furthermore, the combination of these Local Correlation Methods with the Density Fitting approximation turned out to be very powerful. The latter allows for a decomposition of the four-index electron repulsion integrals into three-index objects, eliminating the most severe bottlenecks of previous Local Correlation Methods. Dramatic savings in the computational cost were achieved with this combined method without significant loss in accuracy. In the present project, related local methods for nonconducting crystals are developed. In the spirit of the local ansatz for molecules, well localized Wannier functions (obtained from the Hartree-Fock crystal orbitals) and non-orthogonal projected AOs are used to construct the Fock space. Since many crystals are characterized by rich point symmetry, both translational and point symmetry are exploited to make the calculation feasible, in contrast to the molecular case, where symmetry plays a minor role for extended molecules. Presently, a local MP2 pilot-program for nonconducting crystals has been implemented and a much more efficient program based on Density Fitting is under development. As the next major step, local Coupled Clusters are to be developed.