Modeling of the oxygen defect formation in YCrO3.

Using the pyrolyzing polymer‐salt compositions method yttrium orthochromite (space group Pnma) was synthesized. A value of oxygen nonstoichiometry δ=.056 and a band gap of 1.64 eV were obtained. With the experimentally determined structural parameters as a basis, we performed ab initio simulations to investigate the defect structure of YCrO3±δ. We studied the presence of interstitial oxygen in the YCrO3 at oxygen nonstoichiometry close to the experimental value and vacancies at the same concentration. Formation energies were estimated for interstitial oxygen atoms and compared with those of oxygen vacancies in the cases neutral and charged supercells. The computational results demonstrate that interstitial oxygen is energetically more favorable than the formation of oxygen vacancies. We considered various configurations of the interstitial oxygen atom within the YCrO3 crystal lattice and identified two fundamentally distinct types. An analysis of projected densities of states and charge distributions was performed for these configurations. The results indicate that direct intercalation of oxygen atoms is energetically more favorable than the formation of a peroxide species when the Fermi level is close to the conduction band minimum. [ABSTRACT FROM AUTHOR]