First-Principles Insights into Dopant-Vacancy Interactions in Acceptor-Doped Perovskites

Abstract

Understanding and controlling dopant-vacancy interactions is central to the design of highperformance oxide-ion conductors. Using density functional theory, we systematically examined oxygen vacancy stability in acceptor-doped perovskite oxides (LaAlO₃, LaGaO₃, and SrTiO₃) with substitution at both A and B sites. Enumeration of all symmetry-inequivalent vacancy configurations reveals that, in the absence of first-nearest-neighbor dopants, vacancy energies scale linearly with a simple Coulombic metric defined by dopant-vacancy distances, consistent with electrostatic attraction. Importantly, configurations in which dopants occupy first-nearest-neighbor sites deviate strongly from this electrostatic trend with notably different behavior for A site and B site dopants. Analysis of local structure and bonding uncovers the origin of those deviations from the electrostatic trends. The proximity of an A site dopants could suppress the characteristic umbrella-like lattice relaxation of the BO 6 octahedra that stabilizes isolated vacancies, reducing any elastic component. Concurrently, harder ions on dopant sites lead to loss of partial covalency in adjacent cation-oxygen bonds destabilizing near-neighbor dopant-vacancy configurations. These coupled electrostatic, elastic, and bonding effects govern site-dependent dopant-vacancy interactions and establish a unified physical framework for minimizing vacancy trapping in perovskite oxides.