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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >HO + CO reaction rates and H/D kinetic isotope effects: Master equation models with ab initio SCTST rate constants
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HO + CO reaction rates and H/D kinetic isotope effects: Master equation models with ab initio SCTST rate constants

机译：HO + CO反应速率和H / D动力学同位素效应：具有从头算起SCTST速率常数的主方程模型

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摘要

Ab initio microcanonical rate constants were computed using Semi-Classical Transition State Theory (SCTST) and used in two master equation formulations (1D, depending on active energy with centrifugal corrections, and 2D, depending on total energy and angular momentum) to compute temperature-dependent rate constants for the title reactions using a potential energy surface obtained by sophisticated ab initio calculations. The 2D master equation was used at the P = 0 and P = ∞ limits, while the 1D master equation with centrifugal corrections and an empirical energy transfer parameter could be used over the entire pressure range. Rate constants were computed for 75 K ≤ T ≤ 2500 K and 0 ≤ [He] ≤ 10~(23) cm~(-3). For all temperatures and pressures important for combustion and for the terrestrial atmosphere, the agreement with the experimental rate constants is very good, but at very high pressures and T ≤ 200 K, the theoretical rate constants are significantly smaller than the experimental values. This effect is possibly due to the presence in the experiments of dimers and prereactive complexes, which were not included in the model calculations. The computed H/D kinetic isotope effects are in acceptable agreement with experimental data, which show considerable scatter. Overall, the agreement between experimental and theoretical H/D kinetic isotope effects is much better than in previous work, and an assumption of non-RRKM behavior does not appear to be needed to reproduce experimental observations.
机译：使用半经典过渡状态理论（SCTST）计算了从头算起的微规范速率常数，并将其用于两个主方程式（1D，取决于离心校正的有功能量，而2D，取决于总能量和角动量），以计算温度-通过复杂的从头算得到的势能面，可以得到标题反应的速率常数。在P = 0和P =∞极限下使用2D主方程，而在整个压力范围内可以使用带有离心校正和经验能量传递参数的1D主方程。计算出75 K≤T≤2500 K和0≤[He]≤10〜（23）cm〜（-3）的速率常数。对于对于燃烧和陆地大气而言重要的所有温度和压力，与实验速率常数的一致性非常好，但是在非常高的压力和T≤200 K的情况下，理论速率常数明显小于实验值。这种影响可能是由于实验中存在二聚体和预反应复合物，而模型计算中并未包含这些物质。计算出的H / D动力学同位素效应与实验数据相吻合，后者显示出很大的分散性。总体而言，实验和理论H / D动力学同位素效应之间的一致性比以前的工作要好得多，并且似乎不需要非RRKM行为的假设即可再现实验观察结果。

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