Ring-polymer instanton theory

Instanton theory provides a simple description of a quantum tunnelling process in terms of an optimal tunnelling pathway. The theory is rigorously based on quantum mechanics principles and is derived from a semiclassical approximation to the path-integral formulation. In multidimensional systems, th...

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Bibliographic Details
Published inInternational reviews in physical chemistry Vol. 37; no. 2; pp. 171 - 216
Main Author Richardson, Jeremy O.
Format Journal Article
LanguageEnglish
Published Abingdon Taylor & Francis 03.04.2018
Taylor & Francis Ltd
Subjects
Chemical reactions
Computer simulation
Instanton
Organic chemistry
Polymers
Quantum mechanics
Quantum tunnelling
reaction rate theory
ring polymer
tunnelling
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Summary:Instanton theory provides a simple description of a quantum tunnelling process in terms of an optimal tunnelling pathway. The theory is rigorously based on quantum mechanics principles and is derived from a semiclassical approximation to the path-integral formulation. In multidimensional systems, the optimal tunnelling pathway is generally different from the minimum-energy pathway and is seen to 'cut the corner' around the transition state. A ring-polymer formulation of instanton theory leads to a practical computational method for applying the theory to describe, simulate and predict quantum tunnelling effects in complex molecular systems. It can be used to compute either the rate of a tunnelling process leading to a chemical reaction or the tunnelling splitting pattern of a molecular cluster. In this review, we introduce a unification of the theory's derivation and discuss recent improvements to the numerical implementation.
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ISSN:0144-235X
1366-591X
DOI:10.1080/0144235X.2018.1472353