Harold Friedman and Fernando Raineri are supported by a grant from the Theoretical and Computational Chemistry Program to use a combination of integral equation techniques and molecular dynamics simulations to understand the structural, energetic and dynamical aspects of the solvation of complex molecules in a variety of solvent environments. They have developed a Surrogate Hamiltonian theory that employs a renormalized linear response theory for the nonequilibrium distribution function of the solvent in the time-varying field of the solute. The theory has been applied to number of simpler systems and checked with molecular dynamics simulations. In the next phase of the research, particular emphasis will be placed on electron transfer reactions and bond-breaking / bond-forming reactions. The surrogate Hamiltonian theory will be extended to include higher order effects such as multiple moments, solute excluded volume and hydrogen bonding effects. They also plan to develop a molecular interpretation for the parameters used by physical organic chemists to quantify nucleophilic solvent assistance in the solvolysis of aliphatic halides in solution. The aim of this research project is to improve the way in which measurable properties of solutions are interpreted in terms of the interactions among the molecular constituents. This is particularly challenging for ionic solutions since the long range of the forces between the ionic charges strongly affect both the measurable properties and the mathematical tools needed to relate them to the molecular models. The work of Friedman and Raineri should provide fundamental molecular insight into the mechanism and dynamics of solvation.
