Oxygen vacancy effect on the electronic structure of LaNiO3 using first-principles

While bulk LaNiO3 remains metallic at all temperatures, many experiments show that LaNiO3-x exhibits the metal-insulator transition as the oxygen vacancy level x goes from 0 to 0.5. In addition to the resistivity data, both photoelectron and X-ray absorption spectroscopy works show some intriguing features that cannot be explained based on density functional theory (DFT). In this talk, I will present DFT plus dynamical mean field theory (DMFT) calculations of LaNiO3-x for x=0, 0.25, and 0.5 in different magnetic states. Our DFT+DMFT method was implemented using the maximally localized Wannier function as local orbitals for the correlated subspace. While the DFT density of states (DOS) is similar to experimental spectroscopy data for LaNiO3, it failed to describe the insulating ground state and the peak splitting of unoccupied DOS as x increases to 0.5. Our DFT+DMFT calculations can capture both the resistivity change as well as the spectral features arising from the oxygen vacancy. We find that both the crystal splitting and the Ni d valence changes due to the oxygen vacancy play important roles in explaining the electronic structure. We will also discuss both similarity and difference of vacancy effects between the bulk and ultra-thin film structures.