Superhard orthorhombic phase of B2CO compound

- A lonsdaleite-like orthorhombic structure B2CO (oP8-B2CO) with strong sp3 covalent B‐C and B‐O bonds has been predicted.
- The mechanical, dynamical and thermodynamic stabilities of oP8-B2CO are verified.
- Pressure may promote synthesis of oP8-B2CO.
- oP8-B2CO has a high hardness value of 47.70 GPa.
- oP8-B2CO has the widest band gap (3.540 eV) relative to tP4-B2CO (1.658 eV) and tI16-B2CO (2.988 eV).

A lonsdaleite-like orthorhombic structure B2CO (oP8-B2CO) with strong sp3 covalent B‐C and B‐O bonds has been predicted theoretically by using the crystal structure prediction package CALYPSO. The mechanical, dynamical and thermodynamic stabilities of oP8-B2CO are verified by independent elastic constants, phonon dispersion spectrum and formation enthalpy, respectively. Pressure may promote synthesis of oP8-B2CO, which is demonstrated by calculating the relationship of formation enthalpies for oP8-B2CO via pressure. Based on bond resistance model for hardness, oP8-B2CO has a high hardness value of 47.70 GPa. Band structures calculation illustrates that all B2CO phases are semiconducting with indirect band gaps and oP8-B2CO has the widest band gap (3.540 eV) relative to tP4-B2CO (1.658 eV) and tI16-B2CO (2.988 eV). The superhardness and tunable band gap open an extensive industrial application and scientific research for B2CO compounds.

A lonsdaleite-like orthorhombic B2CO with strong sp3 covalent B‐C and B‐O bonds has been proposed and researched based on first principle calculations. The lonsdaleite-like orthorhombic B2CO is superhard and semiconductor with hardness value of 47.70 GPa and wide band gap 3.540 eV.80