B3LYP exhibits the smallest errors, centered around zero, for the localized valence transitions (Fig. ), although B(30)LYP is somewhat more accurate for the donor → acceptor transitions in Fig. . Favorable performance of B3LYP and PBE0 for other valence excitation energies suggests that 20-25% exact exchange works well for localized valence transitions. In contrast, smaller fractions of exact exchange lead to significant underestimation of the transition energies, culminating in significant and systematic underestimation by GGA functionals. In the present data, this trend manifests as a MAE of 0.3 eV for B(10)LYP as compared to 0.2 eV for both B3LYP and B(20)LYP.