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On the applicability of one- and many-electron quantum chemistry models for hydrated electron clusters

机译：一电子和多电子量子化学模型在水合电子团簇中的适用性

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摘要

We evaluate the applicability of a hierarchy of quantum models in characterizing the binding energy of excess electrons to water clusters. In particular, we calculate the vertical detachment energy of an excess electron from water cluster anions with methods that include one-electron pseudopotential calculations, density functional theory (DFT) based calculations, and ab initio quantum chemistry using MP2 and eom-EA-CCSD levels of theory. The examined clusters range from the smallest cluster size (n = 2) up to nearly nanosize clusters with n = 1000 molecules. The examined cluster configurations are extracted from mixed quantum-classical molecular dynamics trajectories of cluster anions with n = 1000 water molecules using two different one-electron pseudopotenial models. We find that while MP2 calculations with large diffuse basis set provide a reasonable description for the hydrated electron system, DFT methods should be used with precaution and only after careful benchmarking. Strictly tested one-electron psudopotentials can still be considered as reasonable alternatives to DFT methods, especially in large systems. The results of quantum chemistry calculations performed on configurations, that represent possible excess electron binding motifs in the clusters, appear to be consistent with the results using a cavity structure preferring one-electron pseudopotential for the hydrated electron, while they are in sharp disagreement with the structural predictions of a non-cavity model. Published by AIP Publishing.
机译：我们评估量子模型层次结构在表征多余电子与水团簇的结合能方面的适用性。特别是，我们使用包括单电子假电位计算，基于密度泛函理论（DFT）的计算以及使用MP2和eom-EA-CCSD能级从头算量子化学的方法来计算水簇状阴离子中过量电子的垂直脱离能。理论。检查的簇的范围从最小的簇大小（n = 2）到具有n = 1000分子的近纳米大小的簇。使用两个不同的单电子pseudo电位模型，从n = 1000个水分子的簇阴离子的混合量子经典分子动力学轨迹中提取了所研究的簇构型。我们发现，尽管具有较大扩散基集的MP2计算为水合电子系统提供了合理的描述，但应谨慎使用DFT方法，并且仅在仔细进行基准测试后才能使用。经过严格测试的单电子伪电位仍然可以视为DFT方法的合理替代品，尤其是在大型系统中。在构型上进行的量子化学计算结果代表了簇中可能存在的过量电子结合基序，这似乎与使用腔结构（对于水合电子更倾向于单电子pseudo势）的结果相符，但它们与分子结构存在明显分歧。非空洞模型的结构预测。由AIP Publishing发布。

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