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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Collision Efficiency Parameter Influence on Pressure-Dependent Rate Constant Calculations Using the SS-QRRK Theory
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Collision Efficiency Parameter Influence on Pressure-Dependent Rate Constant Calculations Using the SS-QRRK Theory

机译：碰撞效率参数对使用SS-QRRK理论的压力依赖率恒定计算的影响

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摘要

The system-specific quantum Rice-Ramsperger-Kassel (SS-QRRK) theory (J. Am. Chem. Soc. 2016, 138, 2690) is suitable to determine rate constants below the high-pressure limit. Its current implementation allows incorporating variational effects, multidimensional tunneling, and multistructural torsional anharmonicity in rate constant calculations. Master equation solvers offer a more rigorous approach to compute pressure-dependent rate constants, but several implementations available in the literature do not incorporate the aforementioned effects. However, the SS-QRRK theory coupled with a formulation of the modified strong collision model underestimates the value of unimolecular pressure-dependent rate constants in the high-temperature regime for reactions involving large molecules. This underestimation is a consequence of the definition for collision efficiency, which is part of the energy transfer model. Selection of the energy transfer model and its parameters constitutes a common issue in pressure-dependent calculations. To overcome this underestimation problem, we evaluated and implemented in a bespoke Python code two alternative definitions for the collision efficiency using the SS-QRRK theory and tested their performance by comparing the pressure-dependent rate constants with the Rice-Ramsperger-Kassel-Marcus/Master Equation (RRKM/ME) results. The modeled systems were the tautomerization of propen-2-ol and the decomposition of 1-propyl, 1-butyl, and 1-pentyl radicals. One of the tested definitions, which Dean et al. explicitly derived (Z. Phys. Chem. 2000, 214, 1533), corrected the underestimation of the pressure-dependent rate constants and, in addition, qualitatively reproduced the trend of RRKM/ME data. Therefore, the used SS-QRRK theory with accurate definitions for the collision efficiency can yield results that are in agreement with those from more sophisticated methodologies such as RRKM/ME.
机译：特定于系统的量子稻米 - ramseger-Kassel（SS-QRRK）理论（J.AM。Chem。Soc。2016,138,2690）适用于低压限制下方的速率常数。其目前的实现允许在速率恒定计算中包含分析效应，多维隧道和多体扭转Anharmonicity。主方程求解器提供更严格的方法来计算压力依赖性率常数，但文献中提供的几种可用的实现不含有上述效果。然而，与改进的强碰撞模型的配方耦合的SS-QRRK理论低估了高温调节中的单分子压力依赖性速率常数的值，以涉及大分子的反应。这种低估是对碰撞效率的定义的结果，这是能量转移模型的一部分。能量转移模型的选择及其参数构成了压力依赖性计算中的常见问题。为了克服这种低估的问题，我们在定制的Python代码中评估和实施了使用SS-QRRK理论的碰撞效率的两种替代定义，并通过比较与稻米滑坡-Kassel-Marcus的压力相关的速率常数进行测试主方程（RRKM / ME）结果。所建模的系统是普通丙烯-2-醇的互变化，以及1-丙基，1-丁基和1-戊基自由基的分解。其中一个测试定义，Dean等人。明确衍生（Z. physch。Chem.2000,214,1533）纠正了低估了压力依赖率常数，并且此外，规范地复制了RRKM / ME数据的趋势。因此，使用的SS-QRRK理论具有准确的碰撞效率定义可以屈服的结果与来自更复杂的方法（如RRKM / ME）的方法产生达成的结果。

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