Theoretical Study of Novel B2CO Compounds with High Hardness

Abstract Two B2CO phases (oP8’ with sp2-sp3 hybridization coexist and mP16 with unitary sp3 hybridization) were discovered via structure searching and stability analysis. The study of formation enthalpy reveals that high pressure (HP) technology performed maybe an important method for synthesis. Among all isoelectronic with diamond (IED) B-C-O phases, oP8’ has the smallest gap and mP16 has the widest gap. With pressure increasing, for B2CO phases with high symmetry and composed of sp3 hybridization, their band gaps all increases monotonically; for B2CO phases composed by sp3-sp2 hybridization coexist or with low symmetry like mP16, their band gaps increased first and then decreased. oP8’ and mP16 both have large mechanical modulus and they are typical materials with high hardness. Pressure has a positive correlation with its mechanical modulus.