This project in the Theoretical and Computational Chemistry program in the Chemistry Division has two thrusts, first, the development of a new multi-reference coupled-cluster approach for obtaining correlated electronic energies and wave functions for atoms and molecules, and second, the computational implementation of this new approach in the study of mono- and dianions of elemental clusters of the elements carbon, silicon, gallium, and arsenic. The properties of these clusters which are being studied include their structures, their stable and metastable photoexcitations, and their photofragmentation pathways. These clusters may serve as models for solid semiconductor systems. %%% The currently available computational methods for describing the electronic and geometric structures of molecules are in need of considerable improvement to make them both more accurate and reliable as well as cheaper to use. This project involves just such advances, with applications to the study of gas-phase clusters comprised of carbon, silicon, gallium, or arsenic atoms.
