Theoretical investigation of the Al–Cr–B orthorhombic ternary compounds

The Al–Cr–B system is important for the development of oxidation resistant coatings, but fundamental information can rarely be found. In this work, the crystal structure, electronic structure, mechanical properties and Debye temperature of the Al–Cr–B orthorhombic ternary compounds AlCr3B4 and AlCr2B2 compounds at zero pressure have been investigated by means of first-principles calculations based on density functional theory. The bulk modulus B0 and its pressure derivative B′ for both compounds as theoretical values are reported for the first time. The band structure, total density of state (TDOS) and partial density of states (PDOS) for AlCr3B4 and AlCr2B2 are calculated in this work, revealing that both of them exhibit metallic behavior. The mechanical properties have been researched based on the elastic constants, elastic anisotropy, bulk modulus B, shear modulus G, Young’s modulus E, ratio of shear modulus to bulk modulus B/G, microhardness parameter H and Poisson’s ratio ν. The results indicate that the Vickers hardness of AlCr3B4 and AlCr2B2 are about 30 GPa, and the Young’s modulus E values are as high as 492.258 GPa and 487.406 GPa, respectively. Debye temperature (ΘD) of AlCr3B4 is a little higher than that of AlCr2B2.