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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Assessment of theoretical procedures for calculating barrier heights for a diverse set of water-catalyzed proton-transfer reactions
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Assessment of theoretical procedures for calculating barrier heights for a diverse set of water-catalyzed proton-transfer reactions

机译：评估用于计算多种水催化质子转移反应的势垒高度的理论方法的评估

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Accurate electronic barrier heights are obtained for a set of nine proton-transfer tautomerization reactions, which are either (i) uncatalyzed, (ii) catalyzed by one water molecule, or (iii) catalyzed by two water molecules. The barrier heights for reactions (i) and (ii) are obtained by means of the high-level ab initio W2.2 thermochemical protocol, while those for reaction (iii) are obtained using the W1 protocol. These three sets of benchmark barrier heights allow an assessment of the performance of more approximate theoretical procedures for the calculation of barrier heights of uncatalyzed and water-catalyzed reactions. We evaluate initially the performance of the composite G4 procedure and variants thereof (e.g., G4(MP2) and G4(MP2)-6X), as well as that of standard ab initio procedures (e.g., MP2, SCS-MP2, and MP4). We find that the performance of the G4(MP2)-type thermochemical procedures deteriorates with the number of water molecules involved in the catalysis. This behavior is linked to deficiencies in the MP2-based basis-set-correction term in the G4(MP2)-type procedures. This is remedied in the MP4-based G4 procedure, which shows good performance for both the uncatalyzed and the water-catalyzed reactions, with mean absolute deviations (MADs) from the benchmark values lying below the threshold of "chemical accuracy" (arbitrarily defined as 1 kcal mol ~(-1) ≈ 4.2 kJ mol ~(-1)). We also examine the performance of a large number of density functional theory (DFT) and double-hybrid DFT (DHDFT) procedures. We find that, with few exceptions (most notably PW6-B95 and B97-2), the performance of the DFT procedures that give good results for the uncatalyzed reactions deteriorates with the number of water molecules involved in the catalysis. The DHDFT procedures, on the other hand, show excellent performance for both the uncatalyzed and catalyzed reactions. Specifically, almost all of them afford MADs below the "chemical accuracy" threshold, with ROB2-PLYP and B2K-PLYP showing the best overall performance.
机译：对于一组九个质子转移互变异构反应，可以获得准确的电子势垒高度，这些反应要么（i）未催化，（ii）一个水分子催化，要么（iii）两个水分子催化。反应（i）和（ii）的势垒高度是通过高级从头算起的W2.2热化学方案获得的，而反应（iii）的势垒高度则使用W1方案获得的。这三组基准势垒高度可以评估更近似的理论程序的性能，以计算未催化反应和水催化反应的势垒高度。我们首先评估复合G4程序及其变体（例如G4（MP2）和G4（MP2）-6X）以及标准从头程序（例如MP2，SCS-MP2和MP4）的性能。我们发现，G4（MP2）型热化学程序的性能随着参与催化的水分子数量的增加而降低。此行为与G4（MP2）型过程中基于MP2的基础集校正项的不足有关。在基于MP4的G4程序中对此进行了纠正，该程序对未催化反应和水催化反应均显示出良好的性能，与基准值的平均绝对偏差（MAD）低于“化学准确度”的阈值（任意定义为1 kcal mol〜（-1）≈4.2 kJ mol〜（-1））。我们还将检查大量密度泛函理论（DFT）和双混合DFT（DHDFT）程序的性能。我们发现，除少数例外（最著名的是PW6-B95和B97-2）外，对于未催化反应能给出良好结果的DFT程序的性能会随催化中涉及的水分子数量而变差。另一方面，DHDFT程序对于未催化和催化反应均显示出优异的性能。具体而言，几乎所有产品都提供低于“化学准确度”阈值的MAD，其中ROB2-PLYP和B2K-PLYP表现出最佳的整体性能。

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