Superconducting nickelates appear to be difficult to synthesize. Since the chemical reduction of ABO3 (A: rare earth; B transition metal) with CaH2 may result in both, ABO2 and ABO2H, we calculate the topotactic H binding energy by density functional theory (DFT). We find intercalating H is energetically favorable for LaNiO2 but not for Sr-doped NdNiO2. This has dramatic consequences for the electronic structure as determined by DFT+dynamical mean field theory: that of 3d9 LaNiO2 is similar to (doped) cuprates, 3d8 LaNiO2H is a two-orbital Mott insulator. Topotactical H might hence explain why some nickelates are superconducting and others are not.
@article{arxiv.1911.06917,
title = {Topotactic hydrogen in nickelate superconductors and akin infinite-layer oxides ABO2},
author = {Liang Si and Wen Xiao and Josef Kaufmann and Jan M. Tomczak and Yi Lu and Zhicheng Zhong and Karsten Held},
journal= {arXiv preprint arXiv:1911.06917},
year = {2020}
}