Computational Studies of Collision-Induced Polymerization and Thin-Film Growth

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The Theoretical and computational Chemistry Program is supporting Professor Sinnott at the University of Kentucky. This work is also cofunded by funds from the Division of Materials Research. This research will investigate the mechanical and chemical processes which occur when organic molecular clusters impact surfaces at hyperthermal (about 5-80 eV/molecule) and keV incident energies. The approach will be molecular dynamics simulations where the forces on the individual atoms in the clusters and surfaces are obtained from many-body empirical potentials. These results will be checked by repeating the smaller simulations using tight-binding approximation methods and comparing to experiment. This study will provide information about the types of chemical reactions that occur under the high pressure conditions of cluster-solid- surface impacts, detail the mechanisms of these reactions, reveal the types and yields of chemical products, and document any structural changes to the surface. They will also reveal how the chemical reactions depend on a number of factors including surface reactivity and cluster molecular species, size and incident kinetic energy. Cluster-solid-surface collisions are one of the most interesting topics in the area of particle-surface interactions. Some of the possible outcomes include chemical reactions within the cluster to make new chemical products and the growth of thin coatings of the cluster material on the surface. However, there is much that is not known about the chemistry that occurs during such collisions, especially those that involve clusters of carbon and hydrogen, despite the scientific and technological importance of hydrocarbon materials (such as petroleum products and diamond). This research will use computational simulations to investigate the mechanical and chemical processes which occur when these molecular clusters impact surfaces at speeds comparable to those that occur during explosions and in interstellar space. The results will provide information about the types of chemical reactions that occur under the high pressure conditions of cluster-solid-surface impacts and reveal the variety and yields of chemical products. They will also show how the chemical reactions that take place vary with changes in the reaction conditions.