Indenter-angle-sensitive fracture modes and stress response at incipient plasticity

Determination of atomistic fracture modes under different loading conditions is essential to understanding nanomechanics. Here we report first-principles calculations that unveil intriguing indenter-angle-sensitive fracture modes and stress response at the incipient plasticity of strong covalent solids. We show that indenter-angle-dependent distributions of biaxial stresses beneath indenters can produce a variety of bond deformation and breaking patterns that are distinct, at different indenter angles, from each other and from those under a pure shear stress. These results provide key insights for understanding mechanisms of deformation and fracture modes probed by nanoindentation.