Troe J, Ushakov V G, Viggiano A A
Institute for Physical Chemistry, University of Göttingen, Tammannstrasse 6, D-37077 Göttingen, Germany.
J Phys Chem A. 2006 Feb 2;110(4):1491-9. doi: 10.1021/jp0529568.
Statistical adiabatic channel model/classical trajectory (SACM/CT) calculations have been performed for transitional mode dynamics in the simple bond fission reactions of C(6)H(6)(+) --> C(6)H(5)(+) + H and n-C(6)H(5)C(4)H(9)(+) --> C(7)H(7)(+) + n-C(3)H(7). Reduced-dimensionality model potentials have been designed that take advantage of ab initio results as far as available. Average anisotropy amplitudes of the potentials were fitted by comparison of calculated specific rate constants k(E,J) with measured values. The kinetic shifts of the calculated k(E) curves and the corresponding bond energies E(0)(J=0), derived as 3.90 +/- 0.05 eV for C(6)H(6)(+) and 1.78 +/- 0.05 eV for n-C(6)H(5)C(4)H(9)(+), were in good agreement with literature values from thermochemical studies. Kinetic shifts from fixed tight activated complex Rice-Ramsperger-Kassel-Marcus (RRKM) theory, which also reproduces the measured k(E), were larger than the present SACM/CT results as well as earlier results from variational transition state theory (for C(6)H(6)(+)). The approach using RRKM theory was found to underestimate E(0)(J=0) by about 0.2-0.3 eV. A simplified SACM/CT-based method is also proposed which circumvents the trajectory calculations and allows derivation of E(0)(J=0) on the basis of measured k(E) and which provides similar accuracy as the full SACM/CT treatment.
已针对C(6)H(6)(+) --> C(6)H(5)(+) + H和正己基苯正离子（n-C(6)H(5)C(4)H(9)(+)） --> C(7)H(7)(+) + 正丙基（n-C(3)H(7)）的简单键裂变反应中的过渡模式动力学进行了统计绝热通道模型/经典轨迹（SACM/CT）计算。已设计出利用现有从头算结果的降维模型势。通过将计算得到的比速率常数k(E,J)与测量值进行比较，拟合了势的平均各向异性振幅。计算得到的k(E)曲线的动力学位移以及相应的键能E(0)(J = 0)，对于C(6)H(6)(+)得出为3.90 +/- 0.05电子伏特，对于正己基苯正离子得出为1.78 +/- 0.05电子伏特，与热化学研究的文献值吻合良好。来自固定紧密活化络合物的Rice-Ramsperger-Kassel-Marcus（RRKM）理论的动力学位移，其也再现了测量得到的k(E)，比目前的SACM/CT结果以及变分过渡态理论（对于C(6)H(6)(+)）的早期结果更大。发现使用RRKM理论的方法会使E(0)(J = 0)低估约0.2 - 0.3电子伏特。还提出了一种基于SACM/CT的简化方法，该方法规避了轨迹计算，并允许根据测量得到的k(E)推导E(0)(J = 0)，且提供与完整的SACM/CT处理相似的精度。
