  The existence of nanoscale ductility during the fracture of silicate glasses
remains controversial. Here, based on molecular dynamics simulations coupled
with topological constraint theory, we show that nano-ductility arises from the
spatial heterogeneity of the atomic network's rigidity. Specifically, we report
that localized floppy modes of deformation in under-constrained regions of the
glass enable plastic deformations of the network, resulting in permanent change
in bond configurations. Ultimately, these heterogeneous plastic events
percolate, thereby resulting in a non-brittle mode of fracture. This suggests
that nano-ductility is intrinsic to multi-component silicate glasses having
nanoscale heterogeneities.
