From surface segregation to glass-glass interfaces: Composition, activation-energy landscapes, and strength in CuZr nanoglasses

Nanoglasses (NGs) consist of amorphous grains joined by glass-glass interfaces (GGIs), yet the atomic-scale mechanisms by which these interfaces control plasticity remain unsettled. Here, we combine molecular dynamics of ${\mathrm{Cu}}_{64}{\mathrm{Zr}}_{36}$ with the activation-relaxation technique to explicitly sample thermally activated events and map the potential-energy landscape of NGs with distinct interfacial geometries. We find that Cu surface segregation in the precursors persists as a diffuse enrichment at the consolidated interfaces, creating regions of local compositional and structural heterogeneity. Spatially resolved activation-energy distributions reveal that these GGIs host a persistent population of low-barrier excitations largely absent from the bulklike cores. While external strain amplifies the low-energy tail of the distribution, the onset of plasticity is dictated by the intrinsic energetic softness of the interfaces. Macroscopically, this preexisting population of soft sites suppresses abrupt shear localization, leading to a curtailed linear regime and distributed deformation. We further show that variations in mechanical response between architectures are governed by the interfacial volume fraction, while the fundamental deformation mechanism remains invariant. These results quantitatively link interfacial structure to the potential-energy landscape, establishing GGIs as preferred nucleation sites for shear transformations and providing a physics-based foundation for tailoring the mechanical response of amorphous alloys.