Assessment of XC functionals for the study of organic molecules with superhalogen substitution. A systematic comparison between DFT and CCSD(T)

A systematic density functional theory study, including 17 exchange-correlation functionals, was performed on 22 composite structures consisting of organic molecules, e.g., ethylene, ethane, and benzene, and superhalogen substitutions arising from [MgX3](-) and [Mg2X5](-) (X = F, Cl). Range-separated hybrid functionals omega B97M-V, omega B97X-D3(BJ), omega B97XD, omega B97X, and CAM-B3LYP, as well as double-hybrid functionals B2PLYP and DSD-PBEP86-D3(BJ), are verified to provide reliable results with accuracy approaching that at the coupled-cluster single double triple [CCSD(T)] level. The basis set effect of density functional theory calculation is usually moderate, and triple-xi quality, e.g., Def2-TZVP, is enough in most cases. In addition, the average values from HF and MP2 method, indicated as (MP2 + HF)/2, are also quite close to those of CCSD(T). Published under an exclusive license by AIP Publishing.

Automated summary

This study systematically investigates composite structures consisting of organic molecules using various density functional theory methods. The results show that some functionals can provide reliable results with accuracy close to the coupled-cluster single double triple level. The effect of basis set in density functional theory calculations is usually moderate, and triple-xi quality is sufficient in most cases. In addition, the average values from HF and MP2 methods are also close to those of CCSD(T).