Building A Bridge Between AB Initio and Semiempirical Theories of Molecular Electronic Structure

Abstract

The phenomenal increase in computer capabilities, new theoretical developments, and advances in algorithms have sparked a likewise phenomenal increase in the capabilities of ab initio electronic structure methods for accurately describing molecular electronic structure. Thus, ab initio electronic structure computer “packages” are now available to the general scientific community, and their usage is in a rapid stage of growth. While there is a concomitant increase in the sizes of molecules that may be accurately treated with ab initio methods, interesting molecular systems always exist that far exceed the capabilities of the most advanced ab initio electronic structure approaches. Consequently, many approximate and semiempirical electronic structure methods are and must always continue to be necessary for describing the electronic properties of these large systems.