Quantum Tunneling Rates of Gas-Phase Reactions from On-the-Fly Instanton Calculations

Beyer, Adrian N.; Richardson, Jeremy O.; Knowles, Peter J.; Rommel, Judith; Althorpe, Stuart C.

Abstract

The instanton method obtains approximate tunneling rates from the minimum-action path (known as the instanton) linking reactants to the products at a given temperature. An efficient way to find the instanton is to search for saddle-points on the ring-polymer potential surface, which is obtained by expressing the quantum Boltzmann operator as a discrete path-integral. Here we report a practical implementation of this ring-polymer form of instanton theory into the Molpro electronic-structure package, which allows the rates to be computed on-the-fly, without the need for a fitted analytic potential-energy surface. As a test case, we compute tunneling rates for the benchmark H + CH4 reaction, showing how the efficiency of the instanton method allows the user systematically to converge the tunneling rate with respect to the level of electronic-structure theory.

Citation

Beyer, A. N., Richardson, J. O., Knowles, P. J., Rommel, J., & Althorpe, S. C. (2016). Quantum Tunneling Rates of Gas-Phase Reactions from On-the-Fly Instanton Calculations. Journal of Physical Chemistry Letters, 7(21), 4374-4379. https://doi.org/10.1021/acs.jpclett.6b02115

• Journal Article Type: Article
• Acceptance Date: Oct 19, 2016
• Online Publication Date: Oct 19, 2016
• Publication Date: Oct 19, 2016
• Deposit Date: Nov 29, 2016
• Publicly Available Date: Oct 19, 2017
• Journal: Journal of Physical Chemistry Letters
• Electronic ISSN: 1948-7185
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 7
• Issue: 21
• Pages: 4374-4379
• DOI: https://doi.org/10.1021/acs.jpclett.6b02115
• Public URL: https://durham-repository.worktribe.com/output/1369253