Intermediate Ground States of Hydrogen in LaNiO2: A First-Principles Study

Infinite -layer nickelate superconductors R NiO 2 ( R = La, Nd, Pr) are synthesized via chemical reduction using the CaH 2 agent, and the unintentional introduction of H dopant during the reduction process may affect R NiO 2 quality and ultimately determine their electronic properties. However, the ground -state configurations and electronic structures of R NiO 2 under varying H concentrations ( 8 ) remain unclear. In this work, we employ the cluster -expansion method and first -principles calculations to examine the intermediate ground -state structures, electronic structures, and magnetic properties of LaNiO 2 H- 8 (0 < 8 < 1). Interestingly, our results show that H always occupies apical oxygen vacancies, forming ordered H-Ni-H chains along the out -of -plane direction but with different 8 -dependent patterns along the in -plane direction. Notably, the interstitial s -like orbital in the LaNiO 2 host is annihilated by H and the filling of the Ni 3 d bands, especially the 3 d(x) (2) - y (2) and 3 d (z) (2)orbitals, is greatly altered. With H doping, both enhanced magnetic stability of G -type antiferromagnetic states and simultaneous metal -to -insulator transition occur. Our study demonstrates the remarkable doping impact of H in LaNiO 2 , allowing us to gain deeper insight into the structure and superconductivity of infinite -layer nickelates.