Structural origin of intrinsic ductility in binary aluminosilicate glasses

We evaluate the fracture mechanism in the binary aluminosilicate glasses using molecular dynamics simulations. The simulations using two independent force fields reveal that increasing the alumina content promotes shear and suppresses fracture, thereby increasing the intrinsic ductility, in agreement with experimental observations. In indentation simulations, it is directly demonstrated that the deformation mechanism shifts from densification to shear flow with the increase in alumina content. The origin of this intrinsic ductility is that the Al atoms are more amenable to plastic flow and can reduce the creation of lower coordinated weak spots during deformation.