Bimolecular reaction rates from ring polymer molecular dynamics: application to H + CH4 → H2 + CH3.
Bimolecular reaction rates from ring polymer molecular dynamics: application to H + CH4 → H2 + CH3.
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DOI：
10.1063/1.3533275
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发表时间：
2011-01
期刊：
影响因子：
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通讯作者：
Y. V. Suleimanov;R. Collepardo-Guevara;D. Manolopoulos
中科院分区：
文献类型：
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作者：
Y. V. Suleimanov;R. Collepardo-Guevara;D. Manolopoulos
在最近的一篇论文中，我们已经开发了一个有效的实施环聚合物分子动力学（RPMD）方法计算双分子化学反应速率在气相中，并说明它与应用程序的一些基准原子硅藻反应。在本文中，我们表明，同样的方法可以很容易地用于处理更复杂的多原子反应在其全维，如从甲烷的氢提取反应，H + CH（4）→ H（2）+CH（3）。本计算进行了使用修改和重新校准的版本的乔丹-吉尔伯特势能面。200和2000 K之间获得的热速率系数，并与以前的结果相同的势能面。在整个可供比较的温度范围内，RPMD近似与精确的量子力学（多组态含时Hartree）计算相比，与质心密度版本的量子过渡态理论（QTST）或量子瞬子（QI）模型相比，具有更好的一致性。的RPMD速率系数是在深隧穿制度的温度下的确切的量子力学速率系数的2的一个因素。这些结果表明，我们以前的评估原子硅藻反应的RPMD近似的准确性仍然有效的更复杂的多原子反应。他们还建议，QTST和QI速率系数的选择的过渡态划分表面的敏感性成为一个问题，作为反应的维数增加。
In a recent paper, we have developed an efficient implementation of the ring polymer molecular dynamics (RPMD) method for calculating bimolecular chemical reaction rates in the gas phase, and illustrated it with applications to some benchmark atom-diatom reactions. In this paper, we show that the same methodology can readily be used to treat more complex polyatomic reactions in their full dimensionality, such as the hydrogen abstraction reaction from methane, H + CH(4) → H(2) + CH(3). The present calculations were carried out using a modified and recalibrated version of the Jordan-Gilbert potential energy surface. The thermal rate coefficients obtained between 200 and 2000 K are presented and compared with previous results for the same potential energy surface. Throughout the temperature range that is available for comparison, the RPMD approximation gives better agreement with accurate quantum mechanical (multiconfigurational time-dependent Hartree) calculations than do either the centroid density version of quantum transition state theory (QTST) or the quantum instanton (QI) model. The RPMD rate coefficients are within a factor of 2 of the exact quantum mechanical rate coefficients at temperatures in the deep tunneling regime. These results indicate that our previous assessment of the accuracy of the RPMD approximation for atom-diatom reactions remains valid for more complex polyatomic reactions. They also suggest that the sensitivity of the QTST and QI rate coefficients to the choice of the transition state dividing surface becomes more of an issue as the dimensionality of the reaction increases.