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.