Berryman Victoria E J, Boyd Russell J, Johnson Erin R
Department of Chemistry, Dalhousie University , 6274 Coburg Road, Halifax, Nova Scotia Canada , B3H 4R2.
J Chem Theory Comput. 2015 Jul 14;11(7):3022-8. doi: 10.1021/acs.jctc.5b00203.
Predicting the correct ground-state multiplicity for iron(II) porphyrin, a high-spin quintet, remains a significant challenge for electronic-structure methods, including commonly employed density functionals. An even greater challenge for these methods is correctly predicting favorable binding of O2 to iron(II) porphyrin, due to the open-shell singlet character of the adduct. In this work, the performance of a modest set of contemporary density-functional approximations is assessed and the results interpreted using Bader delocalization indices. It is found that inclusion of greater proportions of Hartree-Fock exchange, in hybrid or range-separated hybrid functionals, has opposing effects; it improves the ability of the functional to identify the ground state but is detrimental to predicting favorable dioxygen binding. Because of the uncomplementary nature of these properties, accurate prediction of both the relative spin-state energies and the O2 binding enthalpy eludes conventional density-functional approximations.
预测铁（II）卟啉（一种高自旋五重态）正确的基态多重性，对于包括常用密度泛函在内的电子结构方法而言，仍然是一项重大挑战。由于加合物具有开壳单重态特征，这些方法面临的一个更大挑战是正确预测O2与铁（II）卟啉的有利结合。在这项工作中，评估了一组适度的当代密度泛函近似的性能，并使用巴德离域指数对结果进行了解释。研究发现，在杂化或范围分离的杂化泛函中包含更大比例的哈特里-福克交换具有相反的效果；它提高了泛函识别基态的能力，但不利于预测有利的双氧结合。由于这些性质的不互补性，传统密度泛函近似难以准确预测相对自旋态能量和O2结合焓。
