The brittle-to-ductile transition in aluminosilicate glasses is driven by topological and dynamical heterogeneity

Amorphous materials can exhibit varying degrees of nanoscale ductility depending on their atomic structure. Despite its critical importance for applications, the physical origin that controls ductility remains largely unknown. Here, by using molecular dynamics simulations, we investigate the ductile-to-brittle transition of oxide glasses as a function of the connectivity of the atomic network. Interestingly, based on topological constraint theory, we show that the structural origin of the ductile-to-brittle transition is the rigidity transition caused by the percolation of stressed-rigid atomic clusters. Our further analysis of four-point correlation functions reveals that, similar to the case of supercooled liquids, the plastic dynamics of oxide glasses at room temperature are strongly correlated and spatially heterogeneous. Surprisingly, the dynamical length scale of plastic events significantly decreases when the stressed-rigid cluster percolates, resulting in a narrower transient plastic rearrangement region. These results provide physical insights into the relationship between the topological features of atomic structure, fracture behavior, and stress-induced dynamical heterogeneity of glasses.