The diagonal elements exhibit slight variations within the energy range of 5-20 eV, primarily due to changes in the dipole strength of interband transitions with light polarization, except in the isotropic bixbyite cases. The most significant deviations in the imaginary parts occur in the range of higher interband transitions, specifically between 8-18 eV (see Figs. 12 and 13) resulting in van Hove singularities. The real parts of the dielectric functions (Figs. and) converge to the electronic dielectric tensor ε αβ ∞ as the frequency approaches zero (ω → 0). These values are listed in Table for both DFT and DFT+A -1 /2 calculations and the averaged diagonal values of ε ∞ are provided in Table .