ABSTRACT
This chapter addresses the question of the theoretical prediction and interpretation of experimental spectra obtained by the excitation of valence electrons, such as valence photoemission spectra, bremsstrahlung isochromat spectra, electron energy-loss spectra or absorption spectra. Zirconia is currently of considerable technological interest due to its high strength and stability, even under irradiation, and its excellent dielectric properties. The atomic and electronic structures of zirconia are calculated within density functional theory, and their evolution is analyzed as the crystal-field symmetry changes from tetrahedral to octahedral, to a mixing of these symmetries. The chapter presents new theoretical results for the optical absorption spectra for the different phases, both within the random phase approximation and using time-dependent density functional theory.
