9407309 Schmidt Arizona State Univ. This theoretical study of Monte Carlo methods and applications is supported by the NSF Theoretical and Computational Chemistry Program. Both variational and Greens Function Monte Carlo theory is applied to the calculation of molecular electronic structure and to the study of structure and dynamics of floppy van der Waals clusters. New methodological developments in Monte Carlo theory include: study of explicitly-correlated variational functions for electron correlation effects, use of Greengard's fast multipole method for numerical evaluation of electrostatic potentials, pseudopotentials for inner core electrons, modified fixed node methods, and the combination of Monte Carlo and density functional methods. Both ground and excited states are treated. In particular, the theory is applied to the calculation of spectral shifts for a diatomic or small aromatic molecule in a rare gas cluster. Monte Carlo methods constitute a class of numerical methods for the approximate solution of differential equations using the concept of random walks through the many-dimensional physical space. In this project, Monte Carlo methods are applied to the Schroedinger equation of electrons in atoms and molecules to study electronic spectra and molecular structure. These mathematical methods are also applied to the Schroedinger equation for the large amplitude motions of atoms in loosely bonded molecular clusters.
