TUNNEX: An easy‐to‐use wentzel‐kramers‐brillouin (WKB) implementation to compute tunneling half‐lives

Abstract

Tunneling in experiments (TUNNEX) is a free open-source program with an easy-to-use graphical user interface to simplify the process of Wentzel-Kramers-Brillouin (WKB) computations. TUNNEX aims at experimental chemists with basic knowledge of computational chemistry, and it offers the computation of tunneling half-lives, visualization of data, and exporting of graphs. It also provides a helper tool for executing the zeropoint vibrational energy correction along the path. The program also enables computing high-level single points along the intrinsic reaction path. TUNNEX is available at https://github. com/prs-group/TUNNEX. As the WKB approximation usually overestimates tunneling half-lives, it can be used to screen tunneling processes before proceeding with elaborate kinetic experiments or higher-level tunneling computations such as instanton theory and small curvature tunneling approaches.

Unraveling the catalytic mechanisms of H2 production with thiosemicarbazone nickel complexes

“…This will give the energy at which the protons will attempt to tunnel through the barrier. 28 We also obtained the frequencies of vibration for the two protons, associated with the mode that would bring them together by fitting a parabola to the PES for H–H distances near equilibrium (1.9–2.35 Å). Those frequencies will tell us with which frequency tunnelling will be attempted.…”

“…Nevertheless, such barriers are similarly seen in other intramolecular proton transfer processes. [26][27][28] In those cases, tunnelling is paramount, and could be assessed from the PES using the semi-classical WKB approximation. Details of this approach can be found in the Methodology section and ref.…”

“…29,30 We used BP86, with def2-TZVP as the basis set. [27][28][29][30][31][32][33][34] We used 'Grid4' and 'TightSCF' as our integration and convergence criteria, respectively, following ORCA notation. Solvation effects for DMF were included via CPCM.…”

“…Tunnelling was considered using the WKB approximation, as shown in ref. 28. The probability of tunnelling is given by…”

Simple models for the quick estimation of ground state hydrogen tunneling splittings in alcohols and other compounds

“…[31][32][33] For the latter the release of software is acknowledged which makes the computation of half-lives for tunneling reactions broadly accessible. 34 From the perspective of a spectroscopist (such as the author of the present article), a supplementation with even more approximate methods for quickly and straightforwardly attainable estimations is desirable. Even if they are only robust perhaps to the correct order of magnitude, similar to a Fermi estimate, 35 they already allow to assess whether tunneling might qualify as a plausible explanation for an unexpected spectral splitting.…”