Two B-C-O Compounds: Structural, Mechanical Anisotropy and Electronic Properties under Pressure.

The structural, stability, mechanical, elastic anisotropy and electronic properties of two ternary light element compounds, B₂CO₂ and B₆C₂O₅, are systematically investigated. The elastic constants and phonon calculations reveal that B₂CO₂ and B₆C₂O₅ are both mechanically and dynamically stable at ambient pressure, and they can stably exist to a pressure of 20 GPa. Additionally, it is found that B₂CO₂ and B₆C₂O₅ are wide-gap semiconductor materials with indirect energy gaps of 5.66 and 5.24 eV, respectively. The hardness calculations using the Lyakhov-Oganov model show that B₂CO₂ is a potential superhard material. Furthermore, the hardness of B₆C₂O₅ is 29.6 GPa, which is relatively softer and more easily machinable compared to the B₂CO₂ (41.7 GPa). The elastic anisotropy results show that B₆C₂O₅ exhibits a greater anisotropy in the shear modulus, while B₂CO₂ exhibits a greater anisotropy in Young's modulus at ambient pressure.