Understanding Vibrational Energy Transfer and Spectra in Microporous and Mesoporous Materials

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Ward H. Thompson of the University of Kansas is supported by the Theoretical and Computational Chemistry program and partially supported by the Experimental Program To Stimulate Competitive Research to conduct a theoretical investigation of vibrational energy transfer and spectra in microporous and mesoporous silicate sol-gels. In this work focusing on sol-gel pores, energy transfer processes and vibrational spectra are being simulated, methods for investigating the molecular-level mechanisms are being developed, and the effect of pore size, surface chemistry, and solvent and solute properties are being explored. In this study mixed quantum-classical molecular dynamics simulations, standard perturbation theory approaches, and classical nonequilibrium molecular dynamics simulations are being used to simulate vibrational energy transfer and spectra of neat liquids in sol-gel pores and diatomic and triatomic solutes in solvents confined in sol-gel pores. In addition, approaches for investigating the mechanisms of vibrational energy transfer and spectra and efficiently estimating energy transfer rate constants are being developed. This work will improve the understanding of energy transfer and infrared and Raman measurements in nanostructured porous sol-gels while at the same time accurately computing vibrational spectra and energy transfer rate constants that can be compared with experimental results. It will also yield detailed mechanistic information that will significantly improve the understanding of energy transfer pathways and assist in the interpretation of vibrational spectra in microporous and mesoporous materials. In terms of broader impacts, the results of the proposed work will assist in the design and characterization of microporous and mesoporous materials by improving the understanding of both pathways for energy flow and spectroscopic probes. These are important issues in a wide, and growing, variety of nanostructured systems. Thus, this study will be relevant to spectroscopy, energy transfer, heat flow, and reactivity in materials such as microporous and mesoporous catalysts, supramolecular assemblies, templated materials, reverse micelles, biological systems, hydrogels, membranes, fuel cell electrodes, and nonlinear optical materials. This work should also provide insight into energy dissipation in molecular electronic, optical, and mechanical devices.