Issue 39, 2023

Competing quantum effects in heavy-atom tunnelling through conical intersections

Abstract

Thermally activated chemical reactions are typically understood in terms of overcoming potential-energy barriers. However, standard rate theories break down in the presence of a conical intersection (CI) because these processes are inherently nonadiabatic, invalidating the Born–Oppenheimer approximation. Moreover, CIs give rise to intricate nuclear quantum effects such as tunnelling and the geometric phase, which are neglected by standard trajectory-based simulations and remain largely unexplored in complex molecular systems. We present new semiclassical transition-state theories based on an extension of golden-rule instanton theory to describe nonadiabatic tunnelling through CIs and thus provide an intuitive picture for the reaction mechanism. We apply the method in conjunction with first-principles electronic-structure calculations to the electron transfer in the bis(methylene)-adamantyl cation. Our study reveals a strong competition between heavy-atom tunnelling and geometric-phase effects.

Graphical abstract: Competing quantum effects in heavy-atom tunnelling through conical intersections

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Article information

Article type
Edge Article
Submitted
18 Jul 2023
Accepted
07 Sep 2023
First published
27 Sep 2023
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2023,14, 10777-10785

Competing quantum effects in heavy-atom tunnelling through conical intersections

W. Fang, E. R. Heller and J. O. Richardson, Chem. Sci., 2023, 14, 10777 DOI: 10.1039/D3SC03706A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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