High-density electron doping of SmNiO3 from first principles

Recent experimental work has realized a new insulating state of samarium nickelate (SmNiO3), accessible in a reversible manner via high-density electron doping. To elucidate this behavior, we use the first-principles density functional theory (DFT)+U method to study the effect of added electrons on the crystal and electronic structure of SmNiO3. First, we track the changes in the crystal and electronic structure with added electrons compensated by a uniform positive background charge at concentrations of 14, 12, 34, and 1 electrons per Ni. The change in electron concentration does not rigidly shift the Fermi energy; rather, the added electrons localize on NiO6 octahedra causing an on-site Mott transition and a change in the density of states resulting in a large gap between the occupied and unoccupied Ni eg orbitals at full doping. This evolution of the density of states is essentially unchanged when the added electrons are introduced by doping with interstitial H or Li ions.