Atomistic simulations of pristine and defective hexagonal BN and SiC sheets under uniaxial tension

The uniaxial tensile mechanical properties of pristine and defective hexagonal boron nitride (BN) and silicon carbide (SiC) sheets are investigated through a molecular dynamics finite element method with Tersoff and Tersoff-like potentials. 2-Atom vacancy and 2 types of Stone-Wales defects are considered. It is found that uniaxial tensile stress-strain curves of defective and pristine sheets are almost identical up to fracture points. A centered single defect reduces significantly fracture stress and fracture strain from those of the corresponding pristine sheet. In contrast, Young׳s modulus is nearly unchanged by a single defect. One 2-atom vacancy in the sheet׳s center reduces 15-18% and 16-25% in fracture stress, and 32-34% and 32-48% in fracture strain of BN and SiC sheets, respectively. Reduction in fracture properties depends on the tensile direction as well as the orientation of Stone-Wales defects.