Anharmonicity effects in atom group transfer processes in condensed phases

Abstract

Rate expressions are provided for atom group transfer processes in condensed phases, where both the intramolecular modes associated with the transferring atom group and a continuum of medium modes are strongly reorganized during the process. While the latter modes are described within the usually adopted linear response formalism, the former are represented either by Morse potentials or by a squared hyperbolic tangent potential. These two potentials are appropriate representations for atom group transfer along a stretching and a bending mode, respectively.

Numerical calculations of the Brønsted free energy and the Arrhenius temperature dependence are also presented. The anharmonicity effects are manifested predominantly in the former relationship as a smaller curvature and larger atom group transfer distance as compared with harmonic potentials.