Site occupation disorder study of oxygen vacancies in LaNiO₃

Due to the strong coupling between multiple degrees of freedom, oxygen vacancies in complex oxides lead to a variety of intriguing emergent phenomena. Manipulating oxygen vacancies in strongly correlated rare-earth nickelate perovskites (RNO₃) enables the tuning of their elusive metal-insulator transition (MIT) providing a better handle for band-gap engineering. However, as the number of vacancies in a system increases, the possible configurational space of vacancy structures rises drastically, rendering a computational study of them quite expensive. Here, we study the effects of oxygen vacancies on the electronic properties of the correlated perovskite LaNiO₃ in the R3c space group using a combination of density functional theory and dynamical mean field theory (DFT+DMFT). We utilize a symmetry-adapted configurational ensemble method to obtain a reduced configurational space, thus lowering the computational cost. By treating both Ni-eg and Ni-t2g as correlated orbitals, we show that certain configurations undergo a MIT based on the positioning of their vacancies. We also compare the single oxygen vacancy diffusion energy through means of the nudged elastic band (NEB) method considering non-magnetic (NM), ferromagnetic (FM) and anti-ferromagnetic (AFM-I, AFM-II) ordering.