| This work concerns two important problems in chemical physics: vibrational energy flow in complex environments, and the study of dynamical processes whose rates are slower than those accessible by standard molecular simulation techniques. In collaboration with experimental studies, the effect of local solvation structure on the properties of water vibrations in Cl−·H 2O·Arn (1 ≤ n ≤ 12) clusters was explored using a combination of ab initio electronic structure calculations and electrostatic models. The qualitative behavior of the ionic hydrogen bonded OH stretching vibration was recovered as a function of the number of Ar atoms attached to the cluster.; The phenomenon of vibrational energy pooling in a CO monolayer on a NaCl(100) surface was investigated using a kinetic simulation approach. The kinetic simulation required as input the rate constants for each available channel of vibrational energy flow in the system: laser excitation, vibrational relaxation to the substrate, resonant and non-resonant vibrational energy transfer between nearest neighbor CO molecules on the surface, and fluorescence. These rates were computed using perturbation theory and available experimental information. The results of the simulations agreed favorably with experiment. In addition, a tremendous 13C/12C isotope effect is predicted.; An efficient method for calculating thermal reaction rate constants that can be applied to systems in which transitions from reactant to product occur infrequently was developed. This method does not require the predetermination of reaction coordinates or transition states, and can be applied to systems in which only the stable reactant and product regions are characterized. It was applied to a model for the isomerization of a diatomic in a fluid of repulsive particles, and was able to efficiently compute accurate rate constants even in situations where the barrier to reaction was much larger than kBT. |
