Physical Properties and Electronic Structure of Cr₂B Under Pressure

The physical properties of Cr₂B with I4/m symmetry under pressure are investigated by the first-principles method. With the increase in pressure, the hardness decreases first and then slightly increases, whereas the bulk modulus, shear modulus, Young's modulus, fracture toughness, minimum thermal conductivity, and Debye temperature monotonically increase. Pressure induces the transition from brittleness to toughness at ≈30 GPa. When P > 30 GPa, the hardness and toughness increase simultaneously with pressure. The analysis of electronic structure indicates that the variation of B-B covalent bonds may be responsible for the abnormous increase in hardness when P > 30 GPa.