First-principles insights into dopant–vacancy interactions in acceptor-doped perovskites

Abstract

Understanding and controlling dopant–vacancy interactions is central to the design of high-performance 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 the local structure and bonding uncovers the origin of these deviations from the electrostatic trends. The proximity of an A site dopant could suppress the characteristic umbrella-like lattice relaxation of the BO₆ 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.