Revisiting hydrogen doping in SmNiO₃: A DFT+U and DMFT study

Hydrogen-induced metal-to-insulator transition (MIT) in strongly correlated rare-earth nickelates has opened new directions to explore novel electronic and photonic devices. Although a significant understanding of doping-driven MIT exists, the quantification of doping concentration has remained unclear due to the difficulty in the characterization of hydrogen. Recent experimental work has realized a more significant hydrogen-induced enhancement in resistivity in SmNiO₃ at lower doping concentration, in contrast to the previous understanding where a high doping concentration of 1 hydrogen per Ni atom (H : Ni = 1 : 1) was required to induce the insulating behavior. In the present work, we elucidate this by investigating the effect of various hydrogen doping concentrations on geometry and electronic structures using first-principles density functional theory (DFT)+U and dynamical mean-field theory (DMFT) calculations. We explore all possible H-interstitial configurations for 0.25, 0.5, 0.75, and 1 hydrogen per Ni in the SmNiO₃ unit cell. Further, various H-migration paths are examined using nudged-elastic band calculations. Our findings demonstrate the significance of DMFT calculations to accurately describe the H-induced electronic phase transitions in strongly correlated materials.