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

Abstract

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 C ij 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 TR-OsB4, 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.

Effects of Variable Boron Concentration on the Properties of Superhard Tungsten Tetraboride

“…From our previous diffraction study, the stoichiometry of tungsten tetraboride from the unit cell is ∼WB 4.5 , and thus to probe the stability of theoretically predicted metal tetraboride phases, we kept the boron content fixed and substituted tungsten with other metals. − This will reveal which of the computationally predicted tetraborides are stable; plus, the presence of tungsten should help direct formation. PXRD data for the alloys of W with Ta, Nb, and V prepared with a M:B = 1:4.5 are given in Figures and S3.…”

“…Theoretical calculations have resulted in the prediction of numerous tetraborides. − This has resulted in claims of ReB 4 , OsB 4 , and TaB 4 , all isostructural with tungsten tetraboride. Unfortunately, none of these compounds have yet to be experimentally prepared, and it is possible that these compounds are not stable under equilibrium conditions.…”

Structural Phase Transitions, Electronic Properties, and Hardness of RuB4 under High Pressure in Comparison with FeB4 and OsB4

“…6,10 Recently, the structural transitions sequence of osmium tetraboride (OsB 4 ) has been presented up to 300 GPa. 11,12 At 11 GPa, the P4 2 /nmc phase emerges in OsB 4 similarly resembling FeB 4 . 6 Both FeB 4 and OsB 4 undergo a metal-tosemiconductor phase transition.…”

“…For instance, iron tetraboride (FeB 4 ) exhibits superhard and superconducting properties. , Its high-pressure phases (the tetragonal structures with space groups of I 4 1 / acd and P 4 2 / nmc ) are the semiconducting and hard/superhard materials. , Recently, the structural transitions sequence of osmium tetraboride (OsB 4 ) has been presented up to 300 GPa. , At 11 GPa, the P 4 2 / nmc phase emerges in OsB 4 similarly resembling FeB 4 . Both FeB 4 and OsB 4 undergo a metal-to-semiconductor phase transition.…”