What Makes a Density Functional Approximation Good? Insights from the Left Fukui Function

This work proposes, justifies, and reports tests of the chemically relevant left Fukui function of Li, C, and F on a range of density functional approximations. Analysis indicates that functionals can be good at densities and bad at Fukui functions, and vice versa, analogous with energies and ionization potentials. "TPSSh", "SOGGA11X", and "B2PLYP" are star performers on both, however. Many "Minnesota functionals" fare much better here than in a recent analysis of electron densities. In this context, new optimizing strategies are mentioned.