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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical determination of the rate coefficient for the HO _2+HO _2→H _2O _2+O _s2 reaction: Adiabatic treatment of anharmonic torsional effects
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Theoretical determination of the rate coefficient for the HO _2+HO _2→H _2O _2+O _s2 reaction: Adiabatic treatment of anharmonic torsional effects

机译：HO _2 + HO _2→H _2O _2 + O _s2反应速率系数的理论测定：绝热扭转效应的绝热处理

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摘要

The HO _2 + HO _2 → H _2O _2 + O _2 chemical reaction is studied using statistical rate theory in conjunction with high level ab initio electronic structure calculations. A new theoretical rate coefficient is generated that is appropriate for both high and low temperature regimes. The transition state region for the ground triplet potential energy surface is characterized using the CASPT2/CBS/aug-cc-pVTZ method with 14 active electrons and 10 active orbitals. The reaction is found to proceed through an intermediate complex bound by approximately 9.79 kcal/mol. There is no potential barrier in the entrance channel, although the free energy barrier was determined using a large Monte Carlo sampling of the HO _2 orientations. The inner (tight) transition state lies below the entrance threshold. It is found that this inner transition state exhibits two saddle points corresponding to torsional conformations of the complex. A unified treatment based on vibrational adiabatic theory is presented that permits the reaction to occur on an equal footing for any value of the torsional angle. The quantum tunneling is also reformulated based on this new approach. The rate coefficient obtained is in good agreement with low temperature experimental results but is significantly lower than the results of shock tube experiments for high temperatures.
机译：利用统计速率理论结合高水平的从头算电子结构研究了HO _2 + HO _2→H _2O _2 + O _2的化学反应。产生了适用于高温和低温状态的新的理论速率系数。使用CASPT2 / CBS / aug-cc-pVTZ方法对具有14个活性电子和10个活性轨道的地面三重态势能面的过渡态区域进行了表征。发现该反应通过约9.79kcal / mol的中间配合物进行。尽管自由能垒是使用HO _2方向的大蒙特卡洛采样确定的，但进入通道中没有势垒。内部（紧密）过渡状态低于进入阈值。发现该内部过渡态表现出对应于复合物的扭转构型的两个鞍点。提出了一种基于振动绝热理论的统一处理方法，该方法允许在任何扭转角值下均等地进行反应。量子隧穿也基于这种新方法重新制定。所获得的速率系数与低温实验结果非常吻合，但明显低于高温下冲击管实验的结果。

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