This award supports the participation of Dr. William A. Lester of the University of California, Berkeley, in a program of cooperative research with Dr. Carlton A. Taft of the Brazilian Center of Physics Research in Rio de Janeiro, aimed at investigating the electronic structure, bonding, and other properties of molecules. The electronic properties to be investigated include electronic structure, equilibrium geometry, barriers to rearrangement, and dissociation energies. The consequent improved understanding of molecular properties will be of interest to workers in the fields of chemistry, physics, and biology. This project will make use of the complementary theoretical capabilities of the U.S. and Brazilian groups. The U.S. group has pioneered the development of the quantum Monte Carlo method to determine the energy and other properties of atoms and molecules. In addition, this group has performed calculations of electronic properties using the more approximate, but less expensive, multiconfiguration Hartree-Fock method for larger systems. The Brazilian group focuses on larger systems using Hartree-Fock and generalized valence-bond methods. Thus, methods to deal with various types of molecular systems, as appropriate, are available. In addition to the purely scientific benefit, the collaboration will be beneficial to both groups by providing exposure to very different systems and methods for which the theoretical and computational requirements have previously dictated the need for alternative methods.