Résumé
The fracture of oxide glasses is a subject of high complexity since many factors (e.g. length scale under investigation, strain rate, chemical composition, etc...) play an important role. Using large scale molecular dynamics simulations, we have investigated the composition dependence on the fracture behaviour of sodium silicate glasses on the microscopic scales. While silica glass presents a nearly perfect brittle fracture behaviour, we have found that the one of sodium rich glasses is accompanied by the nucleation of irregular voids as large as 3-4nm ahead of the crack front, indicating the presence of nanoductility for these glasses. We have also explored the spatial and temporal changes of various atomic-level properties and the correlations between them. It has been found that these properties are spatially very heterogeneous with disorder becoming more pronounced for alkali rich compositions. Close to the crack tip, a heating of several hundred degrees above the average temperature has been identified, which permits the structure to relax.