Dynamics of H(2S) + CH(X2 ) reactions based on a new CH2( X ˜ 3 A ″ ) surface via extrapolation to the complete basis set limit

• Published in: Journal of physics. B, Atomic, molecular, and optical physics Atomic, molecular, and optical physics, 2020-05, Vol.53 (9)
• Main Authors: Zhang, Lulu, Liu, Dong, Yue, Daguang, Song, Yuzhi, Meng, Qingtian
• Format: Article
• Language: English
• Subjects: potential energy surface; quasi-classical trajectory method; rate constants
• ISSN: 0953-4075; 1361-6455
• DOI: 10.1088/1361-6455/ab7641

A grid of 5285 ab initio points is utilized to construct a 3D potential energy surface (PES) of the CH 2 ( X ˜ 3 A ″ ) 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 CH 2 ( X ˜ 3 A ″ ) 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 H ( 2 S ) + CH ( X 2 ) → H 2 ( X 1 g + ) + C ( 3 P ) / CH ( X 2 ) + H ( 2 S ) reactions are calculated. It is found that the present ICSs are in good agreement with other theoretical results, and H 2 ( X 1 g + ) + C ( 3 P ) 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.