Ring-polymer molecular dynamics studies on the rate coefficient of the abstraction channel of hydrogen plus ethane, propane, and dimethyl ether.
Ring-polymer molecular dynamics studies on the rate coefficient of the abstraction channel of hydrogen plus ethane, propane, and dimethyl ether.
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DOI：
10.1063/1.4973831
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发表时间：
2017-01
期刊：
影响因子：
--
通讯作者：
Qingyong Meng;Jun Chen
中科院分区：
文献类型：
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作者：
Qingyong Meng;Jun Chen
为了精确计算氢+乙烷（Et）、丙烷（Pr）和二甲醚（DME）的提取通道速率，将环聚合物分子动力学（RPMD）方法与最近构造的母体H + CH4体系的局部置换不变多项式神经网络势能面结合起来[Q. Meng等人，J. Chem.Phys.144，154312（2016）]。对于H + Et，母体系统的CH 4中的一个H原子被甲基取代，而对于H + DME反应，它被甲氧基取代。在H + Pr反应中，用一个乙基取代CH_4中的一个H原子，建立了末端通道，同时用两个甲基取代CH_4中的两个H原子，建立了中间通道.由于标题反应的位能垒必须不同于H + CH_4反应的位能垒，因此必须在完全处理的单重和双重（其中三重贡献由微扰理论计算，即CCSD（T））水平下，通过计算H + CH_4反应与标题反应在耦合簇上的自由能垒之比来进行修正.将目前的RPMD速率与以前的理论和实验结果进行比较，可以发现很好的一致性，并且讨论了目前的RPMD速率与以前的实验结果之间存在偏差的可能原因。
To accurately compute the rates of the abstraction channels of hydrogen plus ethane (Et), propane (Pr), and dimethyl ether (DME), ring-polymer molecular dynamics (RPMD) method is used in conjunction with the recently constructed local permutation invariant polynomial neural-networks potential energy surface of the parent H + CH4 system [Q. Meng et al., J. Chem. Phys. 144, 154312 (2016)]. For H + Et, one of the H atoms in CH4 of the parent system is replaced by a methyl group, while for the H + DME reaction, it is replaced by the methoxyl group. For the H + Pr reaction, replacing one of the H atoms in CH4 by an ethyl group, the terminal channel is built, meanwhile the middle channel is considered through replacing two H atoms in CH4 by two methyl groups. Since the potential energy barriers of the title reactions must differ from the H + CH4 barrier, the corrections have to be made by computing the ratio of free-energy barriers between H + CH4 and the title reactions at coupled cluster with a full treatment singles and doubles (where the triples contribution is calculated by perturbation theory, that is, CCSD(T)) level. Comparing the present RPMD rates with the previous theoretical and experimental results, good agreement can be found. Moreover, probable reasons for the deviation between the present RPMD rates and the previous experimental ones are discussed.