A GENERALIZED LANGEVIN EQUATION STUDY OF THE DYNAMICS OF SUPERIONIC CONDUCTION IN ALPHA-SILVER IODIDE AND ALPHA-COPPER IODIDE
Abstract
The dynamics of ion channeling and activated barrier crossing which underly superionic conduction in (alpha)-AgI and (alpha)-CuI is studied via classical stochastic trajectory simulations based on the molecular time-scale generalized Langevin equation (MTGLE) of motion for condensed phase reaction dynamics. Also presented for comparison purposes are parallel trajectory studies based on the Langevin equation. This comparative study of the MTGLE and Langevin descriptions for activated barrier crossing, allows one to clearly demonstrate the importance of short-timescale dynamical cage effects, which are realistically treated by MTGLE dynamics and not the Langevin dynamics. The implementation of the MTGLE and Langevin equation is based on molecular dynamics simulations of the ionic motion occurring in (alpha)-AgI and (alpha)-CuI. To interpret non-Kramers effects on the channeling kinetics, a new description of the condensed phase effect on activated barrier crossing is developed. This picture emphasizes the competition between "whipback" of the reaction coordinate, arising from instantaneous environmental restoring forces, and frequency-dependent dissipation of reaction coordinate energy due to environmental relaxation.
Degree
Ph.D.
Subject Area
Chemistry
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