Latent Electronic (Anti-)Ferroelectricity in BiNiO_{3}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Materials Science

Background:

• Bismuth nickelate (BiNiO_{3}) exhibits an unusual metal-insulator transition.
• This transition is linked to charge ordering at Bi sites, differing from typical rare-earth nickelates.

Purpose of the Study:

• To elucidate the mechanism behind the Pnma to P1[over ¯] phase transition in BiNiO_{3}.
• To investigate alternative charge ordering phenomena and their implications for ferroelectricity.

Main Methods:

• First-principles calculations were employed to model the electronic structure and phase transitions.
• Analysis of degrees of freedom and energy landscapes was performed.

Main Results:

• An intermediate P2_{1}/m phase was identified during the Pnma to P1[over ¯] transition.
• A nearly degenerate polar Pmn2_{1} ferroelectric phase with significant in-plane polarization (53 μC/cm²) was discovered.
• The Pmn2_{1} phase arises from Bi site charge ordering, distinct from Ni site ordering.

Conclusions:

• BiNiO_{3} is a potential electronic antiferroelectric due to the close energy and low barrier between the Pmn2_{1} and P1[over ¯] phases.
• Strain engineering in thin films can stabilize an electronic ferroelectric ground state.