Size effects on the fracture behavior of amorphous silica from molecular dynamics simulations

Abstract

In this work, the role of structure size and interaction potential on the ductility and mechanical properties of bulk glasses are extensively analyzed using molecular dynamics (MD) simulations. Elastic moduli and mechanical properties for bulk silica structures were calculated from the MD trajectories using three different force fields - diffusive charge reactive potential (DCRP), Teter and Vashishta potentials. These results from MD simulations were compared to experimental measurements and the overall results reassert that, while the elastic moduli show a neglectable variation with structure size, the fracture behavior is considerably affected. Specifically, it is found that the length along the deformation axis is the driver for the brittle to ductile transition. The fracture results, combined with an energy analysis, reveal that the energetic condition for brittle fracture, where elastic strain energy should overcome the fracture surface energy, remains valid for the three potentials.