  Converged approximate density functional calculations usually do not bind
anions, due to large self-interaction error. But Hartree-Fock calculations have
no such prob- lem, producing negative HOMO energies. A recently proposed scheme
for calculating DFT energies on HF densities is shown to work very well for
molecules, better than the common practice of restricting the basis set, except
for cases like CN, where the HF density is too inaccurate due to spin
contamination.
