Kinetics study of the OH + SiH₄ hydrogen abstraction reaction: A theoretical analysis

Abstract

The temperature dependence of the rate constants and the kinetics isotope effects of the OH + SiH4 hydrogen abstraction reaction were theoretically studied. Three different kinetics approaches were used in this study: variational transition state theory with multidimensional tunneling (VTST/MT) corrections, quasi‐classical trajectory (QCT) calculations, and ring polymer molecular dynamics (RPMD). These studies were performed on a global analytical potential energy surface based on explicitly correlated high level ab initio calculations developed in the present work. While the experimental rate constants are practically independent with temperature, the VTST/MT results show a pronounced dependence, the QCT partially corrects this behavior, and RPMD rates are in better agreement with experiment. In this case, in the experimental common temperature range, 300–600 K, the T‐expression for the RPMD rate constants is: k(T) = 6.40 × 10−13.T0.52exp(−0.10/T). The kinetics isotope effects, H/D, are small in this temperature range, revealing the small importance of tunneling effects in this very exothermic and low barrier reaction. Different factors, such as anharmonicity, the zero‐point violation problem or limitations of the surface, without ruling out experimental uncertainties, were analyzed to explain the discrepancies.