First-principles study of electron and hole doping effects in perovskite nickelates

Rare-earth nickelates R$^{3+}$Ni$^{3+}$O$_3$ (R=Lu-Pr, Y) show a striking metal-insulator transition in their bulk phase whose temperature can be tuned by the rare-earth radius. These compounds are also parent phases of newly identified infinite layer RNiO2 superconductors. Although intensive theoretical works have been devoted to understand origin bulk, there only few studies on role hole and electron doping substitutions RNiO$_3$ materials. Using first-principles calculations based density functional theory (DFT) we study effect prototypical nickelate SmNiO3. We perform without Hubbard-like U potential Ni 3d levels but with meta-GGA better amending self-interaction errors. find that at low doping, polarons form intermediate localized states band gap resulting semiconducting behavior. At larger spread more until they merge either valence (hole doping) or conduction (electron band, ultimately metallic state 25% R cation substitution. results reminiscent experimental data available literature demonstrate DFT simulations any empirical parameter qualified for studying effects correlated oxides explore mechanisms underlying superconducting nickelates.