Using molecular statics calculations, sodium silicate glasses are expanded in an isotropic manner to analyze the composition dependence of the mechanical response.
Increasing the amount of sodium makes the systems more ductile. The tensile strength is reduced and the final load bearing strain limit is increased.
Hydrostatic strain hardening appears in the ductile samples. To explain this phenomena, the density is coarse-grained to identify microscopic defects. In samples containing a significant amount of sodium, a large amount of nano-voids appear before reaching the maximum load bearing capacity. In high sodium content silicates these cracks may cause the hardening observed in the pressure results.
In samples with low sodium content, the failure is abrupt and only a large crack is observed. Increasing the amount of long term but weaker Na-O interactions, instead of the short range Si-O ones could explain the observed transition.