THEORETICAL INVESTIGATIONS OF CONDENSED PHASE CHEMICAL DYNAMICS

The molecular timescale generalized Langevin equation (MTGLE) approach to problems in condensed phase chemical dynamics is implemented in simulation studies of chemical reaction dynamics involving solids and in liquid solution. This new approach, which emphasizes the short-time and short-distance scales of chemical reactions in condensed phases, is used as a framework to construct computationally useful and chemically relevant many-body response function modelling techniques, reducing problems in condensed phase chemical dynamics to effective few-body trajectory simulations. The heatbath modelling methods are applied to typical solid and liquid state velocity response functions. The convergence of the heatbath approximants is examined by studying the convergence characteristics of dynamical attributes from gas-solid surface collisions, vibrational energy relaxation in solids and simple atomic recombination in liquids by classical trajectory simulation techniques. Next the approximate MTGLE theory for chemical reactions in liquid solution is numerically implemented and tested. The comparison of approximate results and exact results for the basic MTGLE quantities describing a single solute particle moving in solution provides the motivation for the extension of conventional molecular dynamics (MD) simulation techniques employed in the calculation of the R-dependent MTGLE parameters describing the correlated motions of a pair of interacting solutes. Very useful modelling techniques for these matrix solute configuration-dependent MTGLE quantities are developed and applied to several model systems consisting of molecular iodine in solutions of structureless solvents. Finally, these MTGLE models are used in a numerical investigation of solvent effects on the iodine photodissociation-geminate recombination reaction. The MTGLE approach is found to provide a theoretical framework for studying and understanding many aspects of chemically related motions in condensed phases