Strain-Engineered Formation, Migration, and Electronic Properties of Polaronic Defects in CeO₂

First-principles investigations on the strain-engineered formation, electronic structures, and migration properties of polaronic defects in ceria (CeO₂), including single polarons, oxygen vacancies (Vo²⁺), and polaron–vacancy complexes [(Vo²⁺–1polaron)¹⁺, (Vo²⁺–2polaron)⁰], are reported. Results show that the formation energy of oxygen vacancy increases with both tensile and compressive biaxial strain, whereas the formation energies of polarons and polaron–vacancy complexes reduce (increase) with tensile (compressive) strain, so that their defect concentrations behave drastically different with strain and temperature. Interestingly, due to the distinct deformation potentials, the polaronic defect states can shift toward band edges with strain, beneficial for enhanced electrical conductivity. The migration of polarons in CeO₂ is further explored, and a tendency of strain-induced directional migration is revealed. These findings not only shed light on the fundamental properties of polaronic defects in CeO₂ but also provide an attractive approach of combining defect engineering with strain engineering for oxide-based functional microelectronics, batteries, and catalysts.