Revealing the low-temperature fast relaxation peak in a model metallic glass

The relaxation dynamics and its underlying atomistic mechanism are one of the most important and challenging issues in metallic glasses. Here, we first report a pronounced low-temperature relaxation peak in a model metallic glass, which is located at a much lower temperature than the typical temperature for the conventional β relaxation reported in prior works. Through extensive molecular dynamics simulations, we unravel its intrinsic link with reversible atomic motions, which bridges the vibrational modes and the structural rearrangements governing a normal β relaxation process. Moreover, through the study of the local geometrical anisotropy, we reveal the microscopic mechanism of the fast relaxation process and clearly demonstrate that the fast relaxation dynamics is a trigger to a cascade of critical relaxation modes (such as β and α relaxation). Our findings are of fundamental importance, and further our understanding of the heterogeneous dynamic response of metallic glasses and the dynamic origin of their physical properties.