GENERALIZED TRANSITION-STATE THEORY - CLASSICAL MECHANICAL THEORY AND APPLICATIONS TO COLLINEAR REACTIONS OF HYDROGEN MOLECULES
GENERALIZED TRANSITION-STATE THEORY - CLASSICAL MECHANICAL THEORY AND APPLICATIONS TO COLLINEAR REACTIONS OF HYDROGEN MOLECULES
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DOI：
10.1021/j100471a031
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发表时间：
1979-01-01
影响因子：
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通讯作者：
TRUHLAR, DG
中科院分区：
文献类型：
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作者：
GARRETT, BC;TRUHLAR, DG
我们考虑过渡态理论的三个推广的经典版本：微正则变分过渡态理论，正则变分过渡态理论，和米勒的统一统计理论。证明了微正则变分过渡态理论与绝热反应理论，即绝热过渡态理论是一致的。为了检验这些近似理论的有效性，我们提出了几个共线反应的氢和卤素原子与氢分子的计算。平均反应概率计算使用常规和微正则变分过渡态理论和统一统计理论，并与精确的经典动力学的7种情况下进行比较。这些结果证实了过渡态理论的基本假设在低能下的普遍有效性，并表明变分法可用于将有效性范围扩展到更高的能量。用这些方法和正则变分过渡态理论计算了九个体系的热反应速率常数。采用包含局域振动势阱的二阶和三阶导数的莫尔斯近似，在600 K时，我们计算的七种经典正则速率常数的平均绝对误差和绝对误差范围分别为28和0-78%，10和1-37%为微正则变分理论或绝热过渡态理论，7和1-22%为统一统计理论，15和0-41%为正则变分理论。
We consider classical versions of three generalizations of transition state theory: microcanonical variational transition state theory, canonical variational transition state theory, and Miller's unified statistical theory. We prove that microcanonical variational transition state theory is identical with the adiabatic theory of reactions, ie, to adiabatic transition state theory. To test the validity of these approximate theories, we present calculations for several collinear reactions of hydrogen and halogen atoms with hydrogen molecules. Average reaction probabilities are computed using conventional and microcanonical variational transition state theory and the unified statistical theory and are compared with those of exact classical dynamics for seven cases. These results confirm the general validity of the fundamental assumption of transition state theory at low energy and show that the variational method can be used to extend the range of validity to higher energies. Thermal rate constants are calculated by these methods and by canonical variational transition state theory for nine systems. Using a Morse approximation involving the second and third derivatives of the local vibrational well at its minimum, the average absolute value of the error and range of absolute values of the errors at 600 K for the seven cases where we computed exact classical canonical rate constants are 28 and 0-78% for conventional transition state theory, 10 and 1-37% for the microcanonical variational theory or adiabatic transition state theory, 7 and 1-22% for the unified statistical theory, and 15 and 0-41% for the canonical variational theory.