Dissociation Rate Constant of the Hydrogen Fluoride Dimer by the ab Initio Anharmonic RRKM Theory

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2009-12, Vol.113 (52), p.14664-14669
• Main Authors: Yao, L, Mebel, A. M, Lin, S. H
• Format: Article
• Language: English
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp9044379

The dissociation rate constants for hydrogen fluoride dimers are calculated using the YL method, proposed by Yao and Lin (Yao, L.; Mebel, A. M.; Lu, H. F.; Neusser, H. J.; Lin, S. H. J. Phys. Chem. A 2007, 111, 6722). The dividing surface method and RRKM theory are also used to obtain pseudo-transition states and rate constants, respectively. For the dissociation of HF dimers, the anharmonic rate constants are around 3.02 × 1010 to 3.46 × 1012 s−1, while the harmonic rate constants are in the range of 2.93 × 1010 to 1.66 × 1013 s−1, at a temperature range of 243−1000 K, for the canonical case. For the microcanonical case, the anharmonic rate constants are in the range of 1.91 × 1012 to 1.32 × 1013 s−1 and the harmonic rate constants are in the range of 1.89 × 1012 to 4.93 × 1013 s−1, with a total energy range of 1338−4500 cm−1. Both harmonic and anharmonic rate constants are only comparable to the experimental results 0.5 × 1010 s−1 and 1 × 1011 s−1 in an inert gas bath at room temperature. In this case the harmonic and anharmonic rate constants show similar results in this calculation. The results of this paper indicate that the YL method is suitable for calculating dissociation rate constants of small flexible HF dimers and the anharmonic effect should be included.