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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >An Interpolated ab Initio Quantum Scattering Study of the Temperature Dependence of the CH_3 + HBr → CH_4 + Br Reaction
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An Interpolated ab Initio Quantum Scattering Study of the Temperature Dependence of the CH_3 + HBr → CH_4 + Br Reaction

机译：CH_3 + HBr→CH_4 + Br反应的温度依赖性的插值从头算量子散射研究

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摘要

An interpolated ab initio quantum scattering (AIQS) study for the CH_3 + HBr → CH_4 + Br reaction is presented. The ab initio calculation of energy points has been done using the UMP2/6-311G(3df,d,p) level of theory. Interpolation between the energy points was done using a recently developed generalized discrete variable representation (GDVR) approach. The quantum scattering calculations were performed using a reduced dimensionality rotating line umbrella (RLU) model. The UMP2 results give a vibrationally adiabatic ground-state barrier height of 0.69 kcal/mol for the forward reaction. An unstable van der Waals complex CH_3…HBr was also obtained. This complex plays only a minor role in the reaction dynamics. Calculated thermal rate coefficients show a strong nonlinear Arrhenius behavior. Below 550 K they have a negative temperature dependence, whereas a positive activation energy was obtained at higher temperatures. It was found that placing one quantum of energy in the vibrational mode of the H-Br bond enhances the reactivity, whereas one quantum in the umbrella mode of CH_3 has the opposite effect. Finally, a comparison of calculated thermal rate coefficients with experimental results is made.
机译：提出了CH_3 + HBr→CH_4 + Br反应的插值从头算量子散射（AIQS）研究。能量点的从头算是使用UMP2 / 6-311G（3df，d，p）水平的理论完成的。能量点之间的插值是使用最近开发的广义离散变量表示（GDVR）方法完成的。使用降维旋转线伞（RLU）模型执行量子散射计算。 UMP2结果为正向反应提供了0.69 kcal / mol的振动绝热基态势垒高度。还获得了不稳定的范德华络合物CH_3…HBr。该配合物在反应动力学中仅起次要作用。计算出的热速率系数显示出很强的非线性阿伦尼乌斯行为。低于550 K，它们具有负温度依赖性，而在较高温度下获得正活化能。已经发现，在H-Br键的振动模式中放置一个量子能增强反应性，而在CH_3的伞形模式中放置一个量子则具有相反的作用。最后，将计算出的热速率系数与实验结果进行了比较。

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