Stability and diffusion of oxygen vacancies in LaNiO$_3$: a DMFT study

TL;DR

This study uses DMFT and DFT+U to analyze how oxygen vacancy configurations influence the metal-insulator transition in LaNiO$_3$, revealing that vacancy positioning can tune electronic properties and highlighting differences between DMFT and DFT+U results.

Contribution

It introduces a symmetry-adapted ensemble method to efficiently explore vacancy configurations and compares DMFT with DFT+U for vacancy diffusion energy barriers.

Findings

Controlling vacancy positions tunes the MIT in LaNiO$_3$.

DMFT predicts lower energy barriers than DFT+U due to quantum fluctuations.

Vacancy configuration significantly affects the electronic phase transition.

Abstract

Manipulating oxygen vacancies in strongly correlated rare-earth nickelate perovskites (RNiO$_3$) enables the tuning of their elusive metal-insulator transition (MIT), providing a better handle for control over their electronic properties. In this paper, we investigate the effect of various oxygen vacancy configurations on the MIT of LaNiO$_3$ by studying their spectral functions and the corresponding diffusion energy path using dynamical mean field theory (DMFT) and density functional theory plus U (DFT+U). To consider all possible configurations for a fixed vacancy concentration, we use a symmetry-adapted configurational ensemble method. Within this method, we can reduce the configurational space which needs to be considered, thus lowering the computational cost. We demonstrate that controlling the oxygen vacancy position can tune the occurrence of MIT. We also show that the nudged elastic band (NEB) energy barrier heights and energy profile obtained using DMFT are lower and different than those obtained using DFT+U due to dynamical quantum fluctuations among non-degenerate correlated orbitals not properly treated in DFT+U.