Reinvestigation of Mechanical Properties and Shear -Induced Atomic Deformation of Tetragonal Superhard Semiconducting OsB4

A systematic reinvestigation of the elastic properties, deformation behaviors, and failure characteristics of the recently proposed tetragonal superhard semiconducting compound TR-OsB4, was performed by first-principles calculations to resolve the inconsistency existing in the literature. The single-crystal elastic constants of TR-OsB4 can be perfectly modified using two types of methods, namely, stress strain and energy-strain approaches. Based on the improved C-ij, the derived elastic moduli and theoretical hardness of TR-OsB4, were determined and the obtained hardness is 30.3-30.7 GPa, which is much lower than the previous value of 60 GPa. Studies of elastic anisotropy in combination with ideal tensile strengths indicate that the tetragonal TR-OsB4 shows a strong resistance to tensile deformation along the [110] direction, whereas the weakest peak shear stress of 24.3 GPa along the (100)[001] shear direction is much lower than that of c-BN, indication the lower shear resistance of TROsB4, similarly to the recently synthesized FeB4 and CrB4. Furthermore, evidence of the breaking of atomic bonds in TR-OsB4 under shear deformation was manifested by calculations of the evolution of the electronic structure.