Physical properties of predicted MAX phase borides Hf2AB (A = Pb, Bi): A DFT insight

We have used density functional theory to study the recently predicted MAX phase borides Hf(2)AB (A =Pb, Bi) in which the mechanical, electronic, thermal, and optical properties have been investigated for the first time. A good agreement of the obtained lattice constants with the reported values confirmed the well accuracy of the present calculations. The stiffness constants (C-ij) attest the mechanical stability of all title compounds. The mechanical behaviors have been scrutinized discreetly by considering the bulk modulus, shear modulus, Young's modulus, as well as hardness parameters. The failure mode of Hf(2)AB = Pb, Bi) borides is predicted to be brittle. The electronic band structure and density of states (DOS) revealed the metallic behavior of the titled materials. The anisotropy in electrical conductivity has been disclosed by considering the energy dispersion along different directions. The variation of Vickers hardness is explained in terms of total DOS of Hf(2)AB (A = Pb, Bi). The anisotropic nature of mechanical properties of the phases has also been studied. The technologically important parameters (Debye temperature, minimum thermal conductivity, and Griineisen parameter) have also been used to evaluate the thermal behaviors of the titled materials. The possibility of Hf(2)AB (A = Pb, Bi) for use as coating materials has been assessed by studying the reflectivity.