A. Role of Hartree-Fock exchange DFT/CIS and TD-DFT spectra for an isolated formula unit of TiO 2 are presented in Fig. at the oxygen K edge, using several related functionals with differing amounts of Hartree-Fock exchange. Near-edge features obtained using TD-B3LYP [Fig. ] are off by about 16 eV relative to the experimental edge at 531 eV. TD-CAM-B3LYP does not rectify this in any significant way [Fig. )], whereas TD-SRC1-r1 affords the correct value [Fig. ]. Using the latter as a stand-in for the experimental K-edge, and comparing to either parameterization of DFT/CIS in Fig. , one observes that the DFT/CIS near-edge peaks differ by about 1.9 eV. On the other hand, the DFT/CIS excitation energies are nearly an exact match to those obtained using TD-BH&HLYP [Fig. ], which was certainly not built into the parameterization. This tells us that the absolute accuracy of the K-edge (1s → LUMO excitation) depends sensitively on the fraction of exact exchange. A pronounced intensity difference between B3LYP/CIS and CAM-B3LYP/ CIS is primarily due to inadequacies of the TZVP-based custom basis set that is used in B3LYP/CIS, which is the reason why we rejected that basis set for the new parameterization, opting instead for an up-to-date choice in def2-TZVPD.