Transient Nature of Fast Relaxation in Metallic Glass

Understanding dynamic relaxation in glass is of importance to elucidating phenomena such as deformation, glass transition, diffusion and aging. Unlike other relaxation processes, nearly constant loss (NCL) relaxation is subtle with no well-defined characteristic time and length scales. Prior works attributed possible rattling and caged dynamics as the microscopic mechanism of this structural relaxation, but the origin of the mechanism is still unclear. Through molecular dynamics simulations of a model metallic glass, Cu_64.5 Zr_35.5, we implement dynamic mechanical analysis with atomic level stresses to determine the group of atoms responsible for NCL. Our work demonstrates that NCL is due to transient and varying groups of atoms that participate in the relaxation rather than a specific, single group of atoms causing NCL throughout the simulation.