Theoretical Studies Of Electron Affinities With Density Functional Methods

Electron affinity (EA) is an important property of atoms and molecules, which can fundamentally evaluate the atoms or molecules'ability of gaining an electron. Many experimental and theoretical researchers have focused on them. However, it was difficult to determinate electron affinity by experimental methods. So theoretical predictions of EAs have become more and more important.Due to it's moderate computational consume and high precision, density functional theory has become one of the most important theories in computational chemistry. In this paper, we have examined the performance of 12 density functionals (B3LYP, X3LYP, O3LYP, PBE0, B3PW91, BLYP, OLYP, OPBE, PBE, BPW91,VSXC and TPSS), combined with two basis sets (DZP++ and 6-311+G(3df,2p)) in the prediction of the adiabatic EAs against a set of 91 well-established experimental values.We reach a conclusion that all these modern functionals are generally good, giving a mean absolute deviation (MAD) less than 0.24 eV. B3LYP and X3LYP are among the most reliable methods for this test set. When the DZP++ basis set is adopted, X3LYP is the best with MAD of 0.14 eV, while B3LYP leads to MAD of 0.16 eV. When the basis set is extended to 6-311+G(3df,2p), B3LYP improves its MAD to 0.13 eV, while MAD of X3LYP remains to be 0.14 eV. Most hybrid functionals outperform the corresponding GGA functinals, with the exception of PBE0. The meta-GGA functionals (VSXC and TPSS) are not necessarily better than the GGA functionals. Our calculations also reveal that there are flaws associated with the OPTX exchange functional in the calculations of EA.