Pressure-induced intermetallic valence transition in BiNiO3.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• Bismuth nickelate (BiNiO3) exhibits a unique charge distribution at ambient pressure.
• This material features a distorted perovskite structure with ordered Bi(3+) and Bi(5+) ions.

Purpose of the Study:

• Investigate the valence state change of BiNiO3 perovskite under applied pressure.
• Understand the structural and electronic transitions induced by high pressure.

Main Methods:

• Powder neutron diffraction was employed to study the material's structure.
• Electronic-state calculations were performed to analyze the electronic properties.

Main Results:

• High-pressure experiments revealed a transition from a charge-disproportionated state to a metallic Bi(3+)Ni(3+)O3 phase.
• A pressure-induced charge transfer from Ni to Bi cations was observed.
• The study identified coupled electronic instabilities at both A and B sites.

Conclusions:

• The pressure-induced charge transfer in BiNiO3 is an unprecedented phenomenon.
• This transition leads to a metallic high-pressure phase with potential for diverse ground states.
• A Ni-charge disproportionated state is predicted to be observable under specific conditions.