Stability and Diffusion of Oxygen Vacancies in LaNiO ₃ : A DMFT Study

Oxygen vacancies strongly influence the electronic properties of rare-earth nickelates, enabling the control of their metal–insulator transition (MIT). Here we adopt density functional theory (DFT), DFT + U, and dynamical mean field theory (DMFT) combined with DFT to study the vacancy-induced MIT and diffusion in LaNiO 3 . A symmetry-adapted configurational ensemble approach allows the systematic treatment of distinct vacancy geometries. We find that triple vacancy structures in LaNiO 2.5 can yield either metallic or insulating states depending on the local Ni–O coordination, i.e., octahedral environments favor metallic behavior, while the lower-symmetry geometries can stabilize insulating states. We also compute the migration barrier for a single oxygen vacancy, showing that DMFT predicts significantly lower barriers than DFT + U due to dynamical quantum fluctuations absent in static approaches. These results demonstrate that vacancy configuration and quantum fluctuations jointly govern the MIT and defect dynamics in LaNiO 3, offering new insight for defect engineering and ultrafast electronic switching in correlated oxides.