Atomistic origins of viscoelasticity and β-relaxation in Cu64Zr36 metallic glass and nanoglass

Understanding the structure–property relationships in glasses is challenging due to their inherent structural disorder and non-equilibrium nature. Among these, secondary (β) relaxation plays a vital role in dictating mechanical behavior, yet its structural origins remain elusive. In this study, we employ molecular dynamics simulations to investigate the temperature-dependent viscoelastic properties of Cu64Zr36 in both metallic glass and nanoglass forms. Our results demonstrate that nanoglasses exhibit pronounced β relaxation, manifested as an additional wing near the α peak. String-like atomic motions indicative of β relaxation are prominent in nanoglass, but largely suppressed in metallic glass despite observed correlated displacements. Analysis of local short-range icosahedral and polyheral motifs shows that regions with reduced structural order correspond to greater energy dissipation. These findings provide new atomistic insights into the microscopic mechanisms governing β relaxation and their implications for the mechanical performance of metallic glasses.