Electron densities of homonuclear diatomic molecules as calculated from density functional theory

The electron densities of H-2, Li-2, N-2, O-2, and F-2 have been calculated by density functional theory (DFT) methods with various exchange and correlation functionals such as SVWN, BLYP, B3LYP, BP86, B3P86, and B3PW91 and compared with the results from quadratic configuration interaction calculations including all single and double substitutions (QCISD) using Dunning's correlation consistent polarized valence double- and triple-zeta basis sets augmented with the corresponding diffuse functions (aug-CC-PVDZ and aug-CC-PVTZ). The DFT methods yield electron densities and Laplacians of the densities in good agreement with the QCISD results. The gradient-corrected functionals improve upon the densities calculated by use of the local spin density approximation (SVWN) relative to the corresponding QCISD densities. All gradient-corrected functionals are generally insensitive to the grids used in the study. The basis set, however, has a significant effect on the electron density and shows a strong dependence on the choice of the DFT functionals.