  Superconductivity has recently been observed in Sr-doped NdNiO2 films grown
on SrTiO3. Whether it is caused by or related to the interface remains an open
question. To address this issue, we use density functional theory calculation
and charge transfer self-consistent model to study the effects of polar
discontinuity on the electronic and atomic reconstruction at the NdNiO2/SrTiO3
interface. We find that sharp interface with pure electronic reconstruction
only is energetically unfavorable, and atomic reconstruction is unavoidable. We
further propose a possible interface configuration that contain residual apical
oxygen. These oxygen atoms lead to hybrids of dz2 and dx2-y2 states at the
Fermi level, which weaken the single-band feature and may be detrimental to
superconductivity.
