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首页> 外文期刊>The Journal of Chemical Physics >INTRINSIC NON-RRK BEHAVIOR - CLASSICAL TRAJECTORY, STATISTICAL THEORY, AND DIFFUSIONAL THEORY STUDIES OF A UNIMOLECULAR REACTION
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INTRINSIC NON-RRK BEHAVIOR - CLASSICAL TRAJECTORY, STATISTICAL THEORY, AND DIFFUSIONAL THEORY STUDIES OF A UNIMOLECULAR REACTION

机译：内在非RRK行为-古典轨迹，统计理论和单分子反应的扩散理论研究

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The nonstatistical behavior of a unimolecular reaction at energies well in excess of the threshold is examined. This behavior is sometimes referred to as ''intrinsically non-Rice-Ramsperger-Kassel-Marcus'' (RRKM). It is well known that microcanonical unimolecular rates computed by using classical mechanics can deviate from the predictions of statistical theories, particularly at high energies. The simplest manifestation of this behavior is that rate constants as a function of energy cannot be represented by simple expressions such as the RRK equation, k(E) = nu(1-E*/E)(s-1) with a single set of parameter values over a wide energy range; more specifically, fits of the classical RRK expression to trajectory results frequently yield values for the effective number of degrees of freedom s that an significantly smaller than the ''theoretical'' values 3N-6. In the present study, rates were calculated for the unimolecular dissociation of dimethylnitramine, (CH3)(2)NNO2, by simple N-N bond rupture over wide energy ranges by using classical trajectories and Monte Carlo transition-state theory. The formalism of a diffusional theory of chemical reactions is used to develop a model that relates classical reaction rates to intramolecular vibrational energy redistribution (IVR). This model is based on the assumption that the molecular modes can be separated into reaction coordinate and energy reservoir modes. It is shown how this model can be used to extrapolate high-energy, nonstatistical classical trajectory rates to the low-energy, statistical region. (C) 1996 American Institute of Physics. [References: 45]
机译：检查了单分子反应在远远超过阈值的能量下的非统计行为。这种行为有时被称为“本征上不是Rice-Ramsperger-Kassel-Marcus”（RRKM）。众所周知，使用经典力学计算出的微经典单分子速率可能会偏离统计理论的预测，特别是在高能情况下。此行为的最简单表现是速率常数作为能量的函数无法用简单的表达式来表示，例如RRK方程，k（E）= nu（1-E * / E）（s-1）且具有单个集合在较宽的能量范围内的参数值;更具体地说，经典RRK表达式对轨迹结果的拟合通常会得出有效自由度s的值，该值显着小于3N-6的“理论”值。在本研究中，通过使用经典轨迹和蒙特卡洛过渡态理论，通过简单的N-N键在宽能范围内的断裂，计算了二甲基硝胺（CH3）（2）NNO2的单分子解离速率。化学反应扩散理论的形式主义用于开发将经典反应速率与分子内振动能重新分布（IVR）相关的模型。该模型基于分子模式可以分为反应坐标模式和能量存储模式的假设。展示了如何使用此模型将高能非统计经典轨迹速率外推到低能统计区域。 （C）1996年美国物理研究所。 [参考：45]

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