Theoretical Studies of Kinetics, Dynamics and Mechanisms of Polyatomic Bimolecular Gas Phase Chemical Reactions

理论和计算化学项目正在为犹他大学的Truong教授提供支持。未来三年将进行的研究包括开发和应用新的直接从头算动力学方法来研究气相双分子反应的势能面、动力学和动力学。动力学方法基于变分过渡态理论，并增加了几个多维半经典隧穿修正。反应路径信息将直接从足够精确的从头算或非局域密度泛函方法进行评估，从而消除了构造分析势能函数的需要，而目前所考虑的大多数反应不存在这种势能函数。还将开发一种计算振动态选择速率的方法。这些新方法将被用来研究一些自由基反应的详细动力学。考虑中的大多数反应涉及物种的氢提取，如与H2或甲烷反应的羟基自由基。在这些研究中，将特别注意试剂振动能量对计算的双分子反应速率的影响。这些研究还将试图关联潜在的拓扑结构，对这些反应的动力学和机制的理解在基础和技术层面上都有意义。从技术上讲，这些氢提取反应在燃烧、环境和大气化学中都具有重要意义。根据基本的化学认识，这些反应包含与简单的轻-轻-重(L-L-H)和重-轻-重(H-L-H)原子-硅藻反应相似的反应运动学，其动力学已得到很好的研究。关于这些反应的实验正在不同的实验室进行。因此，从这项工作中得到的势能面信息将有助于解释新的实验观测结果。

The Theoretical and Computational Chemistry program is supporting professor Truong at the University of Utah. The research to be conducted over the next three years involves the development and applications of new direct ab-initio dynamics methods for investigating potential energy surfaces, kinetics, and dynamics of gas-phase bimolecular reactions. The dynamical method is based on Variational Transition State Theory augmented with several multidimensional semiclassical tunneling corrections. Reaction path information will be evaluated directly from a sufficiently accurate ab-initio or non-local density functional method, thus obviating the need for the construction of analytical potential functions which currently do not exist for most of the reactions under consideration. A methodology for calculating vibrational-state selected rates will also be developed. These new methods will be used to study the detailed dynamics of a number of radical reactions. Most of the reactions under consideration involve hydrogen abstraction by species such as hydroxyl radical reacting with H2, or methane. Particular attention will be devoted in these investigations to the effect of reagent vibrational energy on the computed bimolecular reaction rates. These investigations will also attempt to correlate the topology of the potential An understanding of the dynamics and mechanisms of these reactions has implications at both the fundamental as well as technological levels. In terms of technology, these hydrogen abstraction reactions are of significance in combustion, environmental and atmospheric chemistry. In terms of a fundamental chemical understanding, these reactions contain similar reaction kinematics with simple light-light-heavy (L-L-H) and heavy-light-heavy (H-L-H) atom-diatom reactions whose dynamics have been well studied. Experiments on these reactions are underway in different laboratories. Hence, potential energy surface information resulting from this work will be valuable in aiding the interpretations of new experimental observations.