Chromium point defects in hexagonal BaTiO3: A comparative study of first-principles calculations and experiments

Chromium-doped hexagonal barium titanate is studied with first-principles density functional theory. The results are compared with experimental data available from electron paramagnetic resonance, x-ray diffraction, and optical absorption spectra. The probable site for the impurity atom occupancy in the lattice, their probable charge states, and the role of oxygen vacancies in their stabilization are investigated. Defect formation energy is used to analyze the role of electronic-and ionic-compensation mechanisms in stabilizing the point defect. Various atomic positions for the oxygen vacancy surrounding the impurity atom are taken into consideration in order to compare with some of the conclusions derived from experiments. Our results on the substitutional site preference and the location of oxygen vacancy in the next-neighbor surrounding of the impurity Cr are in good agreement with experiments.