Atomistic study of liquid fragility and spatial heterogeneity of glassy solids in model binary alloys

Abstract

Fragility is a fundamental property of glass-forming liquids. Here, we evaluated the liquid fragility and structural and dynamic heterogeneity of glassy solids for four model binary alloys. The most fragile alloy exhibited the maximum dynamic heterogeneity in the mechanical unfreezing process. The local atomic order contributed to structural and dynamic heterogeneities in the glassy solid. We observed that atomic displacement significantly correlated with degrees of clustering of local atomic orders. The clustering produced during the glass-forming quenching process enhanced structural and dynamic heterogeneities, especially in fragile glass alloys. Therefore, this alloy system exhibited correlations among liquid fragility, dynamic heterogeneity in liquid alloys, and dynamic and structural heterogeneities in glassy solids. We discussed the underlying physics of the correlation based on a theoretical model for fragility. These structural and dynamic analyses also provided deeper insights into the features of structural heterogeneity in glassy solids. The alloy with the most fragility exhibited the largest difference in atomic mobility between the densely and loosely packed local atomic orders, implying the greatest heterogeneity in the degree of packing density. Researchers reveal correlations among liquid fragility, dynamic heterogeneity in liquid and glassy solids, and structural heterogeneity in glassy solids using molecular dynamics simulations on binary Cu-Zr alloy models. The study shows that the development of local order in supercooled liquid induces structural heterogeneity in glass solids, affecting fragility. Fragile alloys have a large fraction of densely packed regions and a small fraction of loosely packed regions, with a significant difference in the degree between densely and loosely packed states. This study highlights the connection between liquid fragility and structural heterogeneity in metallic glasses, providing valuable insights for future research and applications. We evaluated the liquid fragility and structural and dynamic heterogeneity of glassy solids. The most fragile alloy exhibited the maximum dynamic heterogeneity in the mechanical unfreezing process. We observed that atomic displacement significantly correlated with degrees of clustering of local atomic orders. The clustering produced during the glass-forming quenching process enhanced structural and dynamic heterogeneities. Therefore, there are correlations among liquid fragility, dynamic heterogeneity in liquid alloys, and dynamic and structural heterogeneities in glassy solids. In addition, the alloy with the most fragility exhibited the largest difference in atomic mobility between the densely and loosely packed local atomic orders.