Hydrogen-Induced Metal-Insulator Transition Accompanied by Inter-Layer Charge Ordering in SmNiO$_3$

TL;DR

This study uses density-functional theory to reveal that partial hydrogen doping induces a stable insulating phase in SmNiO$_3$ through layered charge ordering and Jahn-Teller distortions, clarifying the microscopic mechanism of the transition.

Contribution

It demonstrates that 50% hydrogen doping, not 100%, stabilizes the insulating phase via layered charge disproportionation and structural distortions in SmNiO$_3$.

Findings

50% hydrogen doping induces stable insulating phase.

Layered charge disproportionation of Ni$^{2+}$ and Ni$^{3+}$ observed.

Jahn-Teller distortion causes band gap opening.

Abstract

The microscopic mechanism of the hydrogen-induced metal-insulator transition in SmNiO$_3$ is clarified by means of density-functional theory with the Hubbard U correction. While 100% of hydrogen doping per Ni atom has been supposed to be responsible for the metal-insulator transition, we found that 50% of hydrogen doping results in an outstandingly stable atomic structure showing the insulating property. The stable crystal structure shows the peculiar layered pattern of charge disproportionation of Ni$^{2+}$ and Ni$^{3+}$ valences together with the strong Jahn-Teller distortion that causes the eg orbital state splitting and opens the band gap.