Dynamics of H(2S) + CH(X2Π) reactions based on a new CH2() surface via extrapolation to the complete basis set limit

Abstract

A grid of 5285 ab initio points is utilized to construct a 3D potential energy surface (PES) of the system. In the calculation procedure, the aug-cc-pVXZ (X = Q and 5) basis sets with Davidson correction are employed. The reference wave function for the multi-reference configuration interaction calculations is composed of a full valence complete-active-space self-consistent field wave function. In order to get a more accurate PES, the complete basis set (CBS) limit proposal and the many-body expansion form are used, with the total root mean square deviation of the final CBS-PES being 0.0349 eV. Based on the accurate CBS-PES, the stationary points and vibrational energy levels are obtained and examined in detail, which agree well with other theoretical results. Then, utilizing the CBS-PES and quasi-classical trajectory method, the integral cross-sections (ICSs) and rate constants of the → / reactions are calculated. It is found that the present ICSs are in good agreement with other theoretical results, and is the major product channel. For this channel, the rate constants calculated in this work agree well with experimental and other theoretical results in the high-temperature range. It is worth noting that at room temperature, the theoretical results, including the present work, are consistent with each other, but they are all higher (about 7–10 times) than the experimental result, which implies that a new measurement for the rate constant at room temperature is necessary.