Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
J Chem Phys. 2013 Mar 7;138(9):094307. doi: 10.1063/1.4793394.
The thermal rate coefficients and kinetic isotope effects have been calculated using ring polymer molecular dynamics (RPMD) for the prototypical reactions between methane and several hydrogen isotopes (H, D, and Mu). The excellent agreement with the theoretical rate coefficients of the H + CH4 reaction obtained previously from a multi-configuration time-dependent Hartree calculation on the same potential energy surface provides strong evidence for the accuracy of the RPMD approach. These quantum mechanical rate coefficients are also in good agreement with the results obtained previously using the transition-state theory with semi-classical tunneling corrections for the H∕D + CH4 reactions. However, it is shown that the RPMD rate coefficients for the ultralight Mu reaction with CH4 are significantly smaller than the experimental data, presumably suggesting inaccuracies in the potential energy surface and∕or experimental errors. Significant discrepancies between the RPMD and transition-state theory results have also been found for this challenging system.
使用环聚合物分子动力学（RPMD）计算了甲烷与几种氢同位素（H、D 和 Mu）之间的基元反应的热速率系数和动力学同位素效应。与之前在相同势能面上通过多组态含时哈特ree 计算获得的 H + CH4 反应的理论速率系数非常吻合，这为 RPMD 方法的准确性提供了有力证据。这些量子力学速率系数也与之前使用过渡态理论并对 H∕D + CH4 反应进行半经典隧穿修正得到的结果非常吻合。然而，结果表明，与实验数据相比，RPMD 计算的 Mu 与 CH4 的反应速率系数显著较小，这可能表明势能面和∕或实验误差存在不准确性。对于这个具有挑战性的体系，RPMD 和过渡态理论结果之间也存在显著差异。
