Formation and migration of cation defects in the perovskite oxide LaMnO3

Abstract

Atomistic simulation techniques have been employed to investigate the energetics of cation formation and migration in cubic, rhombohedral and orthorhombic LaMnO ₃ . The calculations suggest that for rhombohedral and orthorhombic lanthanum manganite, oxidative nonstoichiometry leads to the formation of cation vacancies on both La and Mn sites, though tending towards more La vacancies. The activation energy for lanthanum vacancy migration was found to increase with departure from cubic perovskite symmetry in the order: cubic<rhombohedral<orthorhombic. A number of different pathways for manganese vacancy migration were examined. The lowest energy pathway was found to be a curved path between Mn sites that are adjacent along the <100> _cubic directions. Calculated migration energies for this path also increased with distortion from the cubic form. The effect of composition on cation migration energies was also examined.