Non-Markovian rate theory on a multidimensional reaction surface: Complex interplay between enhanced configuration space and memory

Acharya, S and Bagchi, B (2022) Non-Markovian rate theory on a multidimensional reaction surface: Complex interplay between enhanced configuration space and memory. In: Journal of Chemical Physics, 156 (13).

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Abstract

A theory of barrier crossing rate on a multidimensional reaction energy surface is presented. The theory is a generalization of the earlier theoretical schemes to higher dimensions, with the inclusion of non-Markovian friction along both the reactive and the nonreactive coordinates. The theory additionally includes the bilinear coupling between the reactive and the nonreactive modes at the Hamiltonian level. Under suitable conditions, we recover the rate expressions of Langer and Hynes and establish a connection with the rate treatment of Pollak. Within the phenomenology of generalized Langevin equation description, our formulation provides an improvement over the existing ones because we explicitly include both the non-Markovian effects along the reaction coordinate and the bilinear coupling at the Hamiltonian level. At intermediate-to-large friction, an increase in dimensionality by itself tends to reduce the rate, while the inclusion of the memory effects increases the rate. The theory predicts an increase in rate when off-diagonal friction terms are included. We present a model calculation to study isomerization of a stilbene-like molecule using the prescription of Hochstrasser and co-workers on a two-dimensional reaction energy surface, employing Zwanzig-Bixon hydrodynamic theory of frequency-dependent friction. The calculated rate shows a departure from the predictions of Langer's theory and also from the two-dimensional transition state theory. © 2022 Author(s).

Item Type:	Journal Article
Publication:	Journal of Chemical Physics
Publisher:	American Institute of Physics Inc.
Additional Information:	The copyright for this article belongs to American Institute of Physics Inc.
Keywords:	Differential equations; Friction; Surface reactions, Bilinear coupling; Configuration memory; Configuration space; Energy surface; Non-Markovian; Rate theory; Reaction energy; Reaction surfaces; Surface complex; Two-dimensional, Hamiltonians, article; calculation; conformational transition; coworker; cross coupling reaction; friction; human; hydrodynamics; isomerization; memory; phenomenology; prediction; prescription; theoretical study
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	15 May 2022 08:52
Last Modified:	15 May 2022 08:52
URI:	https://eprints.iisc.ac.in/id/eprint/71758

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