Quantum Monte Carlo for the Electronic Structure of Atoms and Molecules

Abstract

Since the late 1960s molecular orbital (MO) theory has dominated the development of ab initio quantum chemistry. Specifically, the Hartree­ Fock-Roothaan (HFR) (1-3) formalism of the self-consistent field (SCF) method, which was greatly facilitated by the development of gaussian basis sets as suggested by Boys (4, 5), and the post-Hartree-Fock methods of configuration interaction (CI) (6-8), multiconfiguration SCF (MCSCF) (9, 10), many-body perturbation theory (MBPT) and coupled-cluster methods (CCM) (11), and Moller-Plesset perturbation theory (MPPT) (12). With the advent of high speed vector supercomputers the field has virtually exploded; larger molecules or very high accuracy for small molecules are now possible. In addition to such capability has come more accurate knowledge of the size of I-particle and N-particle basis sets required for high accuracy (13-16). Not only does the use of large basis sets require large memory and file-storage capability, but HFR and post-HFR algorithms contain significant bottlenecks to vectorization and parallelization. Although many new and efficient matrix methods have been developed