First principles study of electronic and structural properties of CuO

TL;DR

This study uses advanced computational methods to reveal the electronic and structural complexities of CuO, including an orbitally ordered insulating state and various magnetic and orbital configurations influenced by distortions.

Contribution

It introduces a novel application of an extended Hubbard functional to identify an orbitally ordered insulating ground state in cubic CuO, which was previously unreported.

Findings

Identification of an orbitally ordered insulating ground state in cubic CuO

Discovery of multiple magnetic and orbital orders close in energy

Correlation between structural distortions and electronic reorganization

Abstract

We investigate the electronic and structural properties of CuO, which shows significant deviations from the trends obeyed by other transition-metal monoxides. Using an extended Hubbard corrective functional, we uncover an orbitally ordered insulating ground state for the cubic phase of this material, which was expected but never found before. This insulating state results from a fine balance between the tendency of Cu to complete its d-shell and Hund's rule magnetism. Starting from the ground state for the cubic phase, we also study tetragonal distortions of the unit cell (recently reported in experiments), the consequent electronic reorganizations and identify the equilibrium structure. Our calculations reveal an unexpected richness of possible magnetic and orbital orders, relatively close in energy to the ground state, whose stability depends on the sign and entity of distortion.