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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Computational study of the ion-molecule reactions involving fluxional cations: CH4++H-2 - CH5++H and isotope effect
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Computational study of the ion-molecule reactions involving fluxional cations: CH4++H-2 - CH5++H and isotope effect

机译：涉及流动阳离子：CH4 ++ H-2-> CH5 ++ H的离子-分子反应和同位素效应的计算研究

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Potential energy surfaces for the reactions of CH4+ with H-2, HD, and D-2 have been calculated using high-level ab initio methods, including coupled cluster theory, complete active space self-consistent field, and multireference configuration interaction. The energies are extrapolated to the complete basis set limit using the basis sets aug-cc-pVXZ (X = D, T, Q, 5, 6). The CH4+ + H-2 reaction produces CH5+ and H exclusively. Three types of reaction mechanisms have been found, namely, complex-forming abstraction, scrambling, and S(N)2 displacement. The abstraction occurs via a very minor barrier and it is dominant. The other two mechanisms are negligible because of the significant barriers involved. Quantum phase space theory and variational transition state theory are used to calculate the rate coefficients as a function of temperatures in the range of 5-1000 K. The theoretical rate coefficients are compared with the available experimental data and the discrepancy is discussed. The significance of isotope effect, tunneling effect, and nuclear spin effect is investigated. The title reaction is predicted to be slightly exothermic with Delta H-r = -12.7 +/- 5.2 kJ/mol at 0 K.
机译：CH4 +与H-2，HD和D-2反应的势能面已使用高水平的从头算方法进行了计算，包括耦合簇理论，完整的活性空间自洽场和多参考构型相互作用。使用基数组aug-cc-pVXZ（X = D，T，Q，5、6）将能量外推到完整的基数组极限。 CH4 + + H-2反应仅产生CH5 +和H。已经发现了三种类型的反应机制，即复杂形成抽象，加扰和S（N）2置换。抽象是通过很小的障碍发生的，它是主要的。由于涉及重大障碍，其他两种机制可以忽略不计。使用量子相空间理论和变迁过渡态理论来计算速率系数在5-1000 K范围内随温度的变化。将理论速率系数与可用的实验数据进行比较，并讨论差异。研究了同位素效应，隧穿效应和核自旋效应的重要性。预计标题反应在0 K时会稍微放热，Delta H-r = -12.7 +/- 5.2 kJ / mol。

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