First-principles Study of Oxygen Vacancy Formation in Strained Oxides

Based on first-principles density functional theory calculations and chemical bond analyses, we attempted to study the formation of oxygen vacancies (VO) in strained Ti-based oxides. Structural features (e.g., cell volume and mean Ti–O bond length) exhibit a clear and linear correlation with strain. Further, electronic features (e.g., bandgap and Ti–O covalent bond strength) exhibit similar trends for hydrostatic, biaxial, and uniaxial strains, except for shear strains. We investigated the impact of strain on the formation of VO and found that the formation energy in strained oxides was almost linearly linked to changes in the cell volume, bandgap, and Ti–O bond strength of the host oxide, where VO were formed. However, these correlations are not valid in compressively strained systems, which include Ti–O bonds—the bond length being shorter than the sum of Ti and O ionic radii, and shear-strained systems.