Atomic-scale modeling of crack branching in oxide glass

Brittle oxide glasses can easily break into fragments because of crack branching during fracture. The fundamental mechanism underlying this common phenomenon remains controversial. In this study, using atomic-scale simulations with three independent force fields, we directly observe crack branching in silica glass. The critical speed at which the crack branches increases with the critical far field loading. The atomic simulations revealed that crack branching in brittle silica glass is triggered by the nucleation of two or three cavities at different directions ahead of the running crack tip. We compared the simulation results to the cavities observed on the fracture surface in a glass fiber broken under high stress.