Accurate alkynyl radical structures from density functional calculations without Hartree-Fock exchange

作者：Janesko Benjamin G^*; Proynov Emil

来源：Journal of Chemical Physics, 2017, 146(5): 054109.

DOI：10.1063/1.4974986

Density functional approximations (DFAs) often suffer from self-repulsion and delocalization errors which are reduced by exact (Hartree-Fock-like) exchange admixture. Oyeyemi and co-workers recently showed that several DFAs with little exact exchange incorrectly predict bent alkynyl radical geometries, giving errors in ab initio composite methods using density functional theory geometries [V. B. Oyeyemi et al., J. Phys. Chem. Lett. 3, 289 (2012)]. We show that the simple Hartree-Fock-Slater and X alpha DFAs, which have substantial delocalization error, predict linear alkynyl radical geometries without incorporating exact exchange. Our Rung 3.5 DFAs, and rescaled generalized gradient approximations, can give either linear sigma, bent sigma-pi, or nearly linear pi radicals, all without incorporating exact exchange. This highlights the complexity of delocalization error, the utility of accurate empirical DFA geometries for ab initio composite methods, and the insights to be gained from Rung 3.5 DFAs. Published by AIP Publishing.

• 出版日期2017-2-7