Developing Computational Methods and Studying Quantum Dynamics of Molecules and Clusters

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Vladimir Mandelshtam is supported by a grant from the Theoretical and Computational Chemistry Program to develop methods for the study of quantum dynamics in molecules and clusters. His central technique is the filter-diagonalization method, with the utilization of Chebyshev dynamics. Spectra will be computed and analyzed for unimolecular dissociation and recombination processes. Applications include triatomic species such as nitorgen dioxide, formyl radical, and nitrosyl hydride, with emphasis placed on non-adiabatic effects, including Renner-Teller coupling and conical intersections. Longer-term applications include quantum effects in water and argon/hydrogen fluoride clusters. Theoretical studies of chemical dynamics based on accurate quantum mechanical calculations are only possible for small molecules. Therefore such studies play a fundamental role in understanding the dynamics of much larger systems and in relating exising approximate theories to accurate quantum results. Of special interest here are systems with chaotic underlying classical dynamics and high densities of states. A complex quantum dynamics with unassignable spectra offers a challenge even in the case of triatomic molecules.