Phung Quan Manh, Martín-Fernández Carlos, Harvey Jeremy N, Feldt Milica
Department of Chemistry , KU Leuven , Celestijnenlaan 200f , Box 2404, 3001 Leuven , Belgium.
J Chem Theory Comput. 2019 Aug 13;15(8):4297-4304. doi: 10.1021/acs.jctc.9b00370. Epub 2019 Jul 5.
We employed our recently proposed multireference approach CASPT2/CC to calculate the quintet-triplet gaps Δ of a series of non-heme Fe═O species and subsequently used these results to benchmark density functional theory (DFT) as well as two variants of local coupled-cluster approaches (DLPNO-CCSD(T) and LUCCSD(T0)). We showed that current implementations of the local coupled-cluster method are not sufficiently accurate. DLPNO-CCSD(T) systematically overstabilizes the quintet state, whereas LUCCSD(T0) overestimates the triplet one. This sort of systematic bias may be helpful in improving local correlation methods and can also be used as the basis for a simple correction scheme.
我们采用了我们最近提出的多参考方法CASPT2/CC来计算一系列非血红素Fe═O物种的五重态-三重态能隙Δ，随后用这些结果对密度泛函理论（DFT）以及局部耦合簇方法的两种变体（DLPNO-CCSD(T)和LUCCSD(T0)）进行基准测试。我们表明，局部耦合簇方法的当前实现不够准确。DLPNO-CCSD(T)系统性地过度稳定了五重态，而LUCCSD(T0)则高估了三重态。这种系统性偏差可能有助于改进局部相关方法，也可作为一种简单校正方案的基础。
