APPROACH TO DENSITY-FUNCTIONAL IONIZATION-ENERGY

For electronic systems, there are presently only two common ways to ap proximate the exact ionization energy, I, through density-functional t heory, and the two results are often quite different. To improve accur acy, we use coordinate scaling to derive countless ways to approximate I, by observing that I is independent of the charge (coupling constan t) on the electron at fixed ground-state density. To test approximate density functionals, a virial relation is deduced which connects the e xact functional for N electrons with that for (N-1) electrons.