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Quantum Effects on the D + H 3 + → H2D+ + H Deuteration Reaction and Isotopic Variants

AuthorsBulut, Niyazi; Aguado, Alfredo ; Sanz-Sanz, Cristina ; Roncero, Octavio
Issue Date23-Sep-2019
PublisherAmerican Chemical Society
CitationThe journal of physical chemistry, A, Molecules, spectroscopy, kinetics, environment & general theory 123: 8766- 8775 (2019)
AbstractThe title reaction and its isotopic variants are studied using quasi-classical trajectory (QCT) (without taking into account corrections to account for the possible zero point energy breakdown) and ring polymer molecular dynamics (RPMD) methods with a full dimensional and accurate potential energy surface which presents an exchange barrier of approximately 0.144 eV. The QCT rate constant increases when the temperature decreases from 1500 to 10 K. On the contrary, the RPMD rate constant decreases with decreasing temperature, in semiquantitative agreement with recent experimental results. The present RPMD results are in between the thermal and translational experimental rate constants, extracted from the measured data to eliminate the initial vibrational excitation of H , obtained in an arc discharge. The difference between the present RPMD results and experimental values is attributed to the possible existence of non thermal vibrational excitation of H , not completely removed by the semiempirical model used for the analysis of the experimental results. Also, it is found that, below 200 K, the RPMD trajectories are trapped, forming long-lived collision complexes, with lifetimes longer than 1 ns. These collision complexes can fragment by either redissociating back to reactants or react to products, in the two cases tunneling through the centrifugal and reaction barriers, respectively. The contribution of the formation of the complex to the total deuteration rate should be calculated with more accurate quantum methods, as has been found recently for reactions of larger systems, and the present four atoms system is a good candidate to benchmark the adequacy of RPMD method at temperatures below 100 K.
Description10 pags., 8 figs., 2 tabs.
Publisher version (URL)http://dx.doi.org/10.1021/acs.jpca.9b06081
Identifiersdoi: 10.1021/acs.jpca.9b06081
issn: 1520-5215
Appears in Collections:(CFMAC-IFF) Artículos
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