Here, "IE" is the molecule's first ionization energy, computed using a ∆SCF approach, and ε HOMO < 0 is the energy level of the highest occupied molecular orbital (HOMO). Proper asymptotic behavior (for exact KS theory) is υ xc (r) ∼ -1/r, which is recovered from Eq. ( ) provided that the IE theorem of DFT is satisfied, meaning that ε HOMO = -IE .