Oxygen vacancy induced site-selective Mott transition in LaNiO3

Previous experiments show that LaNiO3-x, exhibits the metal-to-insulator transition as the oxygen vacancy level increases.
LaNiO2.5 exhibits a paramagnetic insulating phase, also stabilizing an antiferromagnetic state below T ~ 152K.
Here we study the electronic structure of LaNiO3-x using first-principles.
We find that LaNiO2.5 stabilizes a vacancy-ordered structure with an insulating ground state and the nature of the insulating phase is a ``site-selective" paramagnetic Mott state as obtained using density functional theory plus dynamical mean field theory (DFT+DMFT).
The Ni octahedron site develops a Mott insulating state with strong correlations as the Ni eg orbital is half-filled while the Ni square-planar site with apical oxygen vacancies becomes a band insulator.
Our DFT+DMFT density of states explains that the peak splitting of unoccupied states in LaNiO3-x measured by the experimental X-ray absorption spectra originates from two nonequivalent Ni ions in the vacancy-ordered structure.