Theoretical and Computational Studies of Quantum Dynamical Processes in Condensed Matter Systems

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Gregory Voth is supported by a grant from the Theoretical and Computational Chemistry Program to perform studies of quantum dynamical processes in condensed phase systems. He will employ the dynamical properties of the imaginary time path centroid in the Feynman path integral formulation. The time position correlation function in many-body systems will be computed using centroid molecular dynamics. In this method classical-like equations of motion generate centroid trajectories which are correlated and statistically weighted with the phase space Feynman path integral centroid density. The resulting correlation function can then be related by Fourier transform to the quantum position correlation function. New algorithms will be developed to solve the centroid molecular dynamics equations, and they will be applied to a number of condensed phase studies including: 1) quantum tunneling and mode quantization effects in liquid water; 2) diffusive transport of the hydrated electron in quantized water; and 3) the quantum dynamical motion of an excess proton in water and related systems. Gas phase chemical systems have been studied for a number of years, and excellent theoretical and computational techniques have been developed to model their behavior. More recently theoretical and computational methods are being developed which make it possible to treat more complex condensed phase systems. Most of the current theoretical models are classical in nature, and cannot deal with the additional complications imposed by quantum effects. Voth's research addresses this additional degree of complexity, and proposes the development of computational approaches which will permit the treatment of condensed phase systems which include various quantum degrees of freedom.