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首页> 外文会议>US Combustion Meeting; 20070325-28; San Diego,CA(US) >Association Kinetics of the C_3H_3 + C_3H_3 reaction
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Association Kinetics of the C_3H_3 + C_3H_3 reaction

机译：C_3H_3 + C_3H_3反应的缔合动力学

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Reactions between two resonance stabilized free radicals play an important role in the gas phase chemistry leading to the formation of polycyclic aromatic hydrocarbons and soot in flames burning aliphatic fuels. The theoretical prediction of rate coefficients and product distributions for such reactions is complicated by the fact that the initial complex-formation steps and some dissociation steps are usually barrierless. In this paper, direct variable reaction coordinate transition state theory (VRC-TST) is used to accurately predict the combination kinetics of two propargyl radicals. A set of multifaceted dividing surfaces is used to take into account the multiple possible channels of the C_3H_3 + C_3H_3 reaction. Because of the resonant nature of the reactants their geometric relaxation appears to be important and is calculated for each mutual orientation of the fragments using UB3LYP/cc-pvdz method. The final energy calculations are performed with the CASPT2(10e,10o)/cc-pvdz method. We have also used the VRC- TST approach to calculate the association rate constant and the corresponding number of states for the C_6H_5 + H → C_6H_6 exit channel, which is also barrierless. To this end we have used the CASPT2(2e,2o)/cc-pvdz quantum chemistry method with a one-dimensional CAS+1+2+QC/aug-cc-pvtz correction based on a CH_3 + H reference system. The energy and angular momentum resolved numbers of states for the entrance and C_6H_5 + H exit channels obtained with the VRC-TST approach are used in the related master equation calculation to determine the temperature and pressure dependence of the phenomenological rate coefficients. The total rate constant obtained for the C_3H_3 + C_3H_3 reaction compares favorably with the experimental data available.
机译：两个共振稳定的自由基之间的反应在气相化学中起重要作用，导致燃烧脂肪族燃料的火焰中形成多环芳烃和烟灰。对于这样的反应，速率系数和产物分布的理论预测由于以下事实而变得复杂：初始的复合物形成步骤和某些离解步骤通常是无障碍的。本文采用直接变量反应坐标过渡态理论（VRC-TST）准确预测了两个炔丙基的结合动力学。使用一组多面划分表面来考虑C_3H_3 + C_3H_3反应的多个可能通道。由于反应物的共振性质，它们的几何弛豫似乎很重要，并使用UB3LYP / cc-pvdz方法针对片段的每个相互取向进行计算。使用CASPT2（10e，10o）/ cc-pvdz方法执行最终能量计算。我们还使用了VRC-TST方法来计算关联速率常数和C_6H_5 + H→C_6H_6退出通道的相应状态数，这也是无障碍的。为此，我们使用了基于CH_3 + H参考系统的一维CAS + 1 + 2 + QC / aug-cc-pvtz校正的CASPT2（2e，2o）/ cc-pvdz量子化学方法。通过VRC-TST方法获得的入口和C_6H_5 + H出口通道的能量和角动量解析的状态数，在相关的主方程计算中使用，以确定现象速率系数的温度和压力依赖性。 C_3H_3 + C_3H_3反应获得的总速率常数与可用的实验数据相比具有优势。

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