Trogolo Daniela, Arey J Samuel, Tentscher Peter R
School of Architecture, Civil and Environmental Engineering , École Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland.
Eawag, Swiss Federal Institute of Aquatic Science and Technology , Überlandstrasse 133 , 8600 Dübendorf , Switzerland.
J Phys Chem A. 2019 Jan 17;123(2):517-536. doi: 10.1021/acs.jpca.8b10323. Epub 2019 Jan 4.
Reactions with ozone transform organic and inorganic molecules in water treatment systems as well as in atmospheric chemistry, either in the aqueous phase, at gas/particle interfaces, or in the gas phase. Computed thermokinetic data can be used to estimate the reactivities of molecules toward ozone in cases where no experimental data are available. Although the gas-phase reactivity of olefins with ozone has been characterized extensively in the literature, this is not the case for the richer chemistry of ozone with polar molecules, which occurs in the aqueous phase or in microhydrated environments. Here, we selected a number of model reactions with small molecules (ethene, ethyne, hydrogen cyanide, hydrogen chloride, ammonia, bromide, and trimethylamine) to study the accuracy of different quantum chemical methods for describing the reactivities of these molecules with ozone. We calculated benchmark electronic energies of gas-phase reactions of these systems with single-reference coupled cluster (CC) theory. These benchmark results for the binding energy in the van der Waals complex, the energy of the transition structure, and the reaction energy were estimated to be accurate within 1-2 kcal mol. Singlet oxygen (O) is a common product of ozone reactions. Coupled cluster calculations with up to perturbative quadruples (CCSDT( Q)) were needed to obtain reaction energies accurate within 1 kcal mol when this species was involved. In (micro)hydrated environments or at interfaces, coupled cluster methods are prohibitively expensive in most cases. We tested the suitability of some contemporary density functional theory (DFT) methods to reproduce the benchmark electronic energy differences. Range-separated functionals were found to be promising candidates to estimate forward barrier heights, with LC-ωPBE rivaling the accuracy of CCSD( T). For energies of reaction, however, DFT methods exhibited large systematic errors, depending on their fraction of orbital exchange. This was found to worsen when O is a product, and no safe recommendation can be given for DFT reaction energies in such cases.
在水处理系统以及大气化学中，臭氧反应会在水相、气/颗粒界面或气相中转化有机和无机分子。在没有实验数据的情况下，计算得到的热动力学数据可用于估计分子与臭氧的反应活性。尽管烯烃与臭氧在气相中的反应活性在文献中已有广泛描述，但对于臭氧与极性分子在水相或微水合环境中发生的更丰富的化学反应来说并非如此。在此，我们选择了一些与小分子（乙烯、乙炔、氰化氢、氯化氢、氨、溴化物和三甲胺）的模型反应，以研究不同量子化学方法描述这些分子与臭氧反应活性的准确性。我们用单参考耦合簇（CC）理论计算了这些体系气相反应的基准电子能量。范德华复合物中的结合能、过渡结构的能量和反应能量的这些基准结果估计在1 - 2千卡/摩尔范围内是准确的。单线态氧（O）是臭氧反应的常见产物。当涉及该物种时，需要进行高达微扰四重态的耦合簇计算（CCSDT(Q)）才能获得在1千卡/摩尔范围内准确的反应能量。在（微）水合环境或界面处，耦合簇方法在大多数情况下成本过高。我们测试了一些当代密度泛函理论（DFT）方法再现基准电子能量差的适用性。发现范围分离泛函是估计正向势垒高度的有前途的候选者，其中LC - ωPBE的准确性可与CCSD(T)相媲美。然而，对于反应能量，DFT方法表现出较大的系统误差，这取决于它们的轨道交换分数。当O是产物时，这种情况会恶化，在这种情况下，对于DFT反应能量无法给出可靠的建议。
