Accurate prediction of UV absorption in zirconia-alumina mixed oxide (ZrAl4O8) via GW-BSE calculations.

CONTEXT: Zirconia is a technologically relevant material widely employed in catalysis owing to its thermal stability, acid-base surface properties, and optical response, enabling applications both as a solid acid catalyst and as a photocatalytic material. Even so, the relatively low specific surface area of bulk zirconia may limit its catalytic performance, making supported systems and mixed oxides attractive alternatives for enhancing dispersion and surface accessibility. Among these, zirconia-alumina mixed oxides have attracted significant attention because of the strong interfacial interactions established between both phases, which may involve a migration of Zr4⁺ species into the subsurface region of alumina, leading to the formation of structurally stable mixed oxide domains. This behavior has been associated with modifications in the electronic structure and surface reactivity of the material. In the present work, the UV absorption spectrum of the mixed oxide was calculated, and reasonable agreement was achieved with the measured gap and spectrum, reinforcing the existence of the mixed oxide. The bandgap was determined as 6.47 eV, close to the experimental values, and the simulated spectrum shows good agreement with the experimental profile. METHODS: The geometry of the mixed oxide was optimized with and without constraint at the DFT/PBE level with periodic boundary conditions, a plane-wave basis set for valence electrons, and projected augmented waves (PAW) to treat core electrons. Excited-state optical properties were evaluated by solving the Bethe-Salpeter equation (BSE) on top of GW quasiparticle energies, allowing an accurate description of electron-hole interactions and optical transitions. All calculations were done in VASP software.