CAREER: Unraveling Chemical Consequences of Non-adiabatic Energy Transfer at the Gas-Surface Interface

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Sharani Roy of the University of Tennessee is supported by a CAREER award from the Chemical Theory, Models and Computational Methods program in the Chemistry Division to theoretically investigate the role of nonadiabatic energy transfer in chemical processes at the gas-surface interface. Chemistry at solid surfaces and interfaces is the foundation of a wide range of technologies ranging from heterogeneous catalysis, gas storage, and chemical sensing, to nanoelectronics, nanolithography, and solar cells. It also governs natural phenomena, such as corrosion and oxidation processes, e.g., the rusting of iron and the weathering of rocks. Even interstellar formation of molecules occurs on the surfaces of dust particles. In all the above examples, the fundamental interactions that govern the processes are gas-surface interactions. Each complex surface process is comprised of a series of elementary steps, such as the scattering, adsorption, diffusion, desorption, and reactions of gaseous atoms and molecules on solid surfaces. Therefore, a detailed understanding of the gas-surface interface is essential to explain such diverse surface processes. The Roy group investigates fundamental gas-surface interactions underlying different surface and interface phenomena, with focus on phenomena that involve strong coupling between nuclear motion and electronic motion. This coupling can have important and unexpected consequences on the rates and pathways of chemical processes at surfaces. Dr. Roy's research is integrated with a multi-component education plan that includes the development of courses on computational chemistry, surface chemistry, and high-performance computing in the context of scientific computing. In addition, Dr. Roy plans to organize a symposium on chemical reactions and dynamics at surfaces in collaboration with the Oak Ridge National Laboratory.Theoretical and computational research in surface and interface chemistry often involves studies of chemical dynamics in which the motion of atoms and molecules on surfaces is simulated using classical mechanics. This concept of molecular dynamics (MD) simulations has been very successful in describing gas-surface interactions, and has provided valuable qualitative insight into complicated surface processes. Conventional MD relies on the ubiquitous Born-Oppenheimer or adiabatic approximation, which assumes that nuclear motion is uncoupled from electronic motion. However, there are several fundamentally and industrially important gas-surface systems in which this approximation breaks down. Therefore, it is critical to develop accurate and efficient dynamics methods that can be applied to understand interfacial chemical processes where the adiabatic approximation is weak or invalid. Dr. Roy aims to further develop the 'surface hopping' theoretical method of nonadiabatic dynamics in the context of metal surfaces, and apply it to study strongly nonadiabatic gas-surface phenomena where energy is efficiently transferred between electrons and nuclei. These phenomena include (a) the interaction of hydrogen atoms with a gold surface, (b) the interaction of oxygen atoms with a silver surface, and (c) inelastic electron transport in molecular junctions. The overall goal is to develop a method with broader applicability to surface and interface chemistry that will help to attain a more comprehensive understanding of dynamics beyond the Born-Oppenheimer approximation.