Novel Applications of Mixed Quantum-Classical Dynamics to Studies of Charge and Energy Transfer in Chemical and Biological Systems

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The transport of protons, electrons, and energy plays an instrumental role in many chemical and biological phenomena such as hydrogen bonding, enzyme catalysis, photochemistry, and photosynthesis, and in energy conversion devices such as electrochemical and photovoltaic cells. A fundamental understanding of these transport processes may be achieved through theoretical studies of the underlying molecular dynamics and ultrafast spectroscopic measurements of systems undergoing these processes. Quantum mechanics is required for explaining the dynamics of protons/electrons and energy redistribution. Therefore, any efforts made towards modeling these processes should account for their inherently quantum mechanical nature. Unfortunately, fully quantum mechanical simulations of these processes occurring in environments such as liquids, proteins, polymers, and molecular assemblies, which contain large numbers of atoms, are not possible on today’s fastest computers. To dramatically cut down the computational costs, in these cases, one can treat a small number of particles directly associated with the transport quantum mechanically, while the remaining particles can be treated using classical Newtonian mechanics to a good approximation. Our goal is to apply such mixed quantum-classical approaches for simulating the dynamics and ultrafast spectra of a variety of charge and energy transfer processes in chemical and biological systems of fundamental and technological importance (i.e. photo-induced electron transfer, proton-coupled electron transfer, and vibrational energy transport), and thereby shed new light on ways of controlling them to increase the efficiency and efficacy of solar energy harvesting materials, catalysts for water splitting and solar fuels production, and molecular electronics applications. We will focus on control methods, which rely on varying the properties of the classical part of the system, or coupling the quantum part to light fields whose properties can be easily tuned. The results of these studies will ultimately lead to principles for designing devices that can reduce Canada's dependence on fossil fuels or be used in Canada’s electronics industry.