Boron Suboxide and Boron Subphosphide Crystals: Hard Ceramics That Shear without Brittle Failure

摘要: Boron suboxide (B_6O), boron carbide (B_4C), and related materials are superhard. However, they exhibit low fracture toughness, which limits their engineering applications. Here we show the shear deformation mechanism of B_6O using density functional theory along most plausible slip system (0111)/ . We discovered an unusual phenomenon in highly sheared recovers its original crystal structure, indicates possibility being to a large strain without failure. also found similar structural recovery subphosphide (B_(12)P_2) for shearing same system. In contrast, components B_4C, brittle These novel mechanisms under high conditions suggest that key element designing ductile hard is couple icosahedra via one- or two-atom chains allow by walking intericosahedral bonds chain alternately accommodate fracturing icosahedra.