Density functional theory calculations for F−

The orbital energy of F− with local DFT functionals is re-examined. Unlike previous researchers, our calculations give negative 2p orbital energies with LDA and BLYP. In order to obtain this result, it was essential to use a numerical integration grid that would give accurate Kohn–Sham matrix elements for very diffuse basis functions. We suggest that DFT programs should test for the accuracy of the self-overlap of basis functions, computed by numerical integration, rather than just testing the accuracy of the integral of the total density.