Zhang Liling, Lu Yunpeng, Lee Soo-Y, Zhang Dong H
Department of Chemistry, National University of Singapore, Kent Ridge, Singapore 119260, Singapore.
J Chem Phys. 2007 Dec 21;127(23):234313. doi: 10.1063/1.2812553.
Transition state wave packet calculations have been carried out to obtain the thermal rate constants for the H+CH(4) reaction on the Jordan-Gilbert potential energy surface. The eight-dimensional model for the X+YCZ(3) type of reaction was employed by restricting the nonreacting CZ(3) group under a C(3V) symmetry. We calculated the cumulative reaction probability for the total angular momentum J=0, from which the thermal rate constants were obtained for the temperature range between 250 and 500 K by employing the J-K shifting approximation. It is found that the eight-dimensional rate constants agree very well with the seven dimensional ones, in which the CH bond length in the nonreacting CH(3) group is fixed, suggesting that the additional mode for the symmetry stretching in CH(3) group does not have any important effect on the reaction within the temperature range considered here. The present transition state wave packet results agree well with rate constants obtained from the previous seven dimensional initial state selected wave packet study, indicating the consistence of the treatments involved in these two studies. On the other hand, it is found that the energy threshold for the cumulative reaction probability for J=0 from the present study is higher than that from the full dimensional multiconfiguration time-dependent Hartree study by about 0.06 eV, resulting in severe discrepancy between the present rate constants and the multiconfiguration time-dependent Hartree results.
已进行过渡态波包计算，以获得约旦 - 吉尔伯特势能面上H + CH(4)反应的热速率常数。对于X + YCZ(3)型反应，采用八维模型，通过将非反应性CZ(3)基团限制在C(3V)对称性下。我们计算了总角动量J = 0时的累积反应概率，通过采用J - K位移近似，在此基础上获得了250至500 K温度范围内的热速率常数。结果发现，八维速率常数与七维速率常数非常吻合，在七维模型中，非反应性CH(3)基团中的CH键长是固定的，这表明CH(3)基团中对称伸缩的额外模式在此处考虑的温度范围内对反应没有任何重要影响。目前的过渡态波包结果与先前七维初始态选择波包研究获得的速率常数吻合良好，表明这两项研究中所涉及的处理方法具有一致性。另一方面，发现本研究中J = 0时累积反应概率的能量阈值比全维多组态含时哈特里研究的结果高约0.06 eV，导致本研究的速率常数与多组态含时哈特里结果之间存在严重差异。
