Fracture of sodium-silicate glasses: Insights from atomistic computer simulations
Résumé
Understanding the fracture behavior of glasses at the atomic scale is of fundamental impor-
tance for improving the mechanical properties of these materials. Using an interaction potential
that has been parametrized via ab initio calculations [1,2], we have carried out molecular dy-
namics simulations in order to investigate the influences of system size, sample geometry, and
strain rate on the fracture behavior of sodium silicate glasses. In contrast to earlier simulation
studies on fracture, in which the bulk glass sample has often been put directly under stress, we
have applied here uniaxial tension to a glass sample that has stress-free surfaces, i.e. we adopt
a setup that is close to the one used in experiments on fracture studies. Our results show that
the used interatomic potential captures reasonably well the brittle fracture on the nanoscale of
silica glass and the enhanced ductility when sodium oxide is added to the glass network. We
have found that below a critical strain rate of around 0.5/ns the stress-strain curve remains
basically unchanged. By investigating the formation, growth and coalescence of cavities in the
strained glass samples we find that in sodium silicate glasses the formation of cavities is being
more pronounced than in silica glass. The analysis of atomic energy, local stress and strain, and
atomic displacements have confirmed the presence and the development of mechanically weak
zones in the glass network, resulting in paths along which the cracks advance.
A. Carré, S. Ispas, J. Horbach, and W. Kob, ”Developing empirical potentials from ab initio
simulations: The case of amorphous silica,” Comput. Mater. Sci., vol. 124, pp. 323–334, Nov.
2016.
S. Sundararaman, L. Huang, S. Ispas, and W. Kob, ”New optimization scheme to obtain inter-
action potentials for oxide glasses”, to be sumitted (2017)