Mechanical properties of 2D blue phosphorus and temperature effect.

Blue phosphorus is an emerging 2D material that exhibits finite electronic band gap and may find promising applications in advanced semiconducting devices. Comparing to its allotrope, black phosphorus, mechanical properties of blue phosphorus have not been explored in detail. Here we report molecular dynamics simulations of mechanical responses of blue phosphorus under uniaxial tensile, biaxial tensile and shear loadings. It is found that blue phosphorus shows less anisotropic effect as compared to black phosphorus, the room temperature Young's modulus is about 122.3 GPa and 121.6 GPa along armchair and zigzag directions, respectively, shear modulus is about 27.1 GPa and 28.6 GPa, respectively, along armchair and zigzag directions. Temperature effect on mechanical responses is also systematically studied within a range of 5-400 K. It is found that temperature reduces both Young's modulus and fracture strain and fracture strength of blue phosphorus, owing to the interplay between thermal energy and strain energy applied to the models. Brittle fracture mode is found in blue phosphorus in all loading conditions, with varied crack nucleation and propagation modes. The role of strain rate on the mechanical properties is examined and found to systematically modify the ultimate stress and ultimate strain of BlueP. Structural details including bond length and bond angle variations to external strain are analyzed to gain deeper insights into the underlying mechanisms.