Density functional theory study of native point defects in CaO

We investigate the structural, electronic, and optical properties of native point defects in CaO using first-principles density functional calculations. Oxygen vacancies (VO) are favored under O-poor conditions, whereas calcium vacancies (VCa) dominate under O-rich conditions. Calculated migration barriers and binding energies indicate that VCa–VO complexes are thermodynamically stable and can survive high-temperature annealing. Optical transition energies, evaluated using the Franck–Condon framework, suggest that several experimentally observed absorption and emission peaks can be attributed to negatively charged VCa–VO complexes as well as isolated oxygen vacancies.