Professor Clifford Dykstra is supported by a grant from the Theoretical and Computational Chemistry Program to continue his research on the analysis of dynamical features of weakly bound complexes. Ab initio electronic structure calculations are used for evaluating the intrinsic electrical response properties of molecules. The results of these calculations are incorporated into a molecular mechanics model for clusters which can then be used to predict molecular structures of larger clusters. A new feature of this work is the incorporation of diffusion quantum Monte Carlo methodology to improve the predictions of dynamical properties. The primary goal of the work is a detailed, fundamental understanding of weak interactions, including transferable potentials, electronic structure changes, and dynamical manifestations. Weak molecular interactions are important in problems ranging from molecular clustering, certain surface phenomena, nonlinear optical response of aggregations, aspects of protein structure, and drug design. This work is aimed at achieving reliable predictive capability for structures and energetics of weak clusters, and for the changes in properties of systems which experience weak inter- and intramolecular interactions such as hydrogen-bonding.
