From NdNiO₂ to a Mott Multiferroic BiNiO₂

Motivated by the recently discovered superconductivity in Sr-doped nickelate oxides NdNiO2 reduced from NdNiO3 in experiments, we predict a Mott multiferroic BiNiO2 that may be obtained from BiNiO3. There is a ferroelectric structural transition for BiNiO2 from the nonpolar phase to the polar phase with the P4mm space group, which is driven by the lone pair on Bi. The lowest energy ground-state for polar BiNiO2 is a Hubbard Mott insulator with the G-type antiferromagnetic spin configurations. The replacement of Nd by Bi serves as a connecting link between a parent compound of high-temperature superconductor and a Mott multiferroic.