Void deformation and breakup in shearing silica glass

We study shear deformation and breakup of voids in silica glass using molecular dynamics simulations. With an increase in the shear strain, two kinds of defects-threefold-coordinated silicon and nonbridging oxygen atoms-appear as spherical voids deform elastically into ellipsoidal shapes. For shear strains ε>15%, nanocracks appear on void surfaces and voids deform plastically into a threadlike structure. Nanocracks are nucleated by the migration of threefold-coordinated Si and nonbridging O on Si-O-Si-O rings. For ε>40%, the threadlike structures break up into several fragments. © 2009 The American Physical Society.