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

理论与计算化学项目支持犹他大学的张教授。该研究将在未来三年内进行，包括开发和应用新的直接从头算动力学方法，用于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，并辅以若干多维半经典隧穿修正。反应路径信息将直接通过足够精确的从头算或非局部密度泛函方法进行评估，从而避免了构建分析势函数的需要，而目前大多数正在考虑的反应都不存在分析势函数。还将开发一种计算振动状态选择率的方法。这些新方法将用于研究一些自由基反应的详细动力学。考虑到的大多数反应都涉及到氢的吸收，如氢氧自由基与H2或甲烷的反应。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。这些研究也将试图将电位的拓扑结构联系起来。对这些反应的动力学和机制的理解在基础和技术层面都有意义。从技术上讲，这些抽氢反应在燃烧化学、环境化学和大气化学中具有重要意义。在基本的化学理解方面，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，这些反应的动力学已经得到了很好的研究。不同的实验室正在对这些反应进行实验。因此，从这项工作中得到的势能表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.