First principles study on hydrogen doping induced metal-to-insulator transition in rare earth nickelates RNiO3 (R = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Yb)

Abstract

Rare earth nickelates (RNiO₃), consisting of a series of correlated transition metal oxides, have received increasing attention due to their sharp metal-to-insulator transition (MIT). Previous reports focused on understanding the origin and modulation of thermally driven MIT by strain effects, cation doping, or external electric field. Recently, it was reported that isothermal chemical doping of hydrogen can induce MIT and increase resistivity by ∼8 orders of magnitude, which opens up the possibility of utilizing these oxides to develop advanced electronic and sensing devices. In this study, we applied first principles methods to study geometric and electronic structures of MIT driven by hydrogen doping in a series of rare earth nickelates RNiO₃ (R = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Yb). Hybrid functional HSE06 calculations predict that all oxides under study exhibit sharp MIT, opening up an ∼3 eV band gap after hydrogen doping, with band gap values slightly increasing from Pr to Yb. We find that the R site elements play a key role in determining hydrogen adsorption energies and hydrogen migration barriers, which controls how difficult it would be for the hydrogen atoms to migrate inside the oxides. Detailed information on geometries, electronic structures, migration barriers and adsorption energies of hydrogen provides guidance for further optimizing these materials for future experiments and applications.