Nguyen Huyen Thi, Hang Tran Dieu, Nguyen Minh Tho
Computational Chemistry Research Group, Ton Duc Thang University , Ho Chi Minh City, 778000 Vietnam.
Faculty of Applied Sciences, Ton Duc Thang University , Ho Chi Minh City, 778000 Vietnam.
J Phys Chem A. 2017 Feb 9;121(5):1032-1040. doi: 10.1021/acs.jpca.6b11665. Epub 2017 Jan 27.
High-accuracy calculations were performed to study the mechanisms of the reactions between the diatomic silicon monoxide (SiO) with NH and CH. These reactions are relevant to the SiO-related astrochemistry and atmospheric chemistry as well as the activation of the N-H and C-H bonds by the SiO triple bond. Energetic data used in the construction of potential energy surfaces describing the SiO + NH/CH reactions were obtained at the coupled-cluster theory with extrapolation to the complete basis set limit (CCSD(T)/CBS) using DFT/B3LYP/aug-cc-pVTZ optimized geometries. Standard heats of formation of a series of small Si-molecules were predicted. Insertion of SiO into the N-H bond is exothermic with a small energy barrier of ∼8 kcal/mol with respect to the SiO + NH reactants, whereas the C-H bond activation by SiO involves a higher energy barrier of 45 kcal/mol. Eight product channels are opened in the SiO + NH reaction including dehydrations giving HNSi/HSiN and dehydrogenations. These reactions are endothermic by 16-119 kcal/mol (calculated at 298.15 K) with the CCSD(T)/CBS energy barriers of 21-128 kcal/mol. The most stable set of products, HNSi + HO, was also the product of the reaction pathway having lowest energy barrier of 21 kcal/mol. Ten product channels of the SiO + CH reaction including decarbonylation, dehydration, dehydrogenation, and formation of Si + CHOH are endothermic by 19-118 kcal/mol with the energy barriers in the range of 71-126 kcal/mol. The formation of HCSiO + HO has the lowest energy barrier of 71 kcal/mol, whereas the most stable set of products, SiH + CO, is formed via a higher energy barrier of 90 kcal/mol. Accordingly, while SiO can break the N-H bond of ammonia without the assistance of other molecules, it is not able to break the C-H bond of methane.
进行了高精度计算，以研究双原子一氧化硅（SiO）与NH和CH之间的反应机理。这些反应与SiO相关的天体化学和大气化学以及SiO三键对N-H和C-H键的活化作用有关。用于构建描述SiO + NH/CH反应的势能面的能量数据是在耦合簇理论下，使用DFT/B3LYP/aug-cc-pVTZ优化几何结构并外推至完全基组极限（CCSD(T)/CBS）获得的。预测了一系列小硅分子的标准生成热。SiO插入N-H键是放热反应，相对于SiO + NH反应物，其能垒较小，约为8 kcal/mol，而SiO对C-H键的活化作用涉及45 kcal/mol的较高能垒。SiO + NH反应开启了八个产物通道，包括生成HNSi/HSiN的脱水反应和脱氢反应。这些反应在298.15 K下计算时吸热16 - 119 kcal/mol，CCSD(T)/CBS能垒为21 - 128 kcal/mol。最稳定的产物组HNSi + HO也是反应途径中能垒最低（21 kcal/mol）的产物。SiO + CH反应的十个产物通道，包括脱羰、脱水、脱氢以及生成Si + CHOH，吸热19 - 118 kcal/mol，能垒在71 - 126 kcal/mol范围内。HCSiO + HO的形成具有71 kcal/mol的最低能垒，而最稳定的产物组SiH + CO则通过90 kcal/mol的较高能垒形成。因此，虽然SiO在没有其他分子协助的情况下可以断裂氨的N-H键，但它无法断裂甲烷的C-H键。
