Metallic glass-forming systems exhibit complex dynamic behaviors during the glass transition. Understanding the dynamic nature of metallic glasses and supercooled liquids is a crucial issue in the study of glassy physics. Topological order provides a novel perspective for re-examining the dynamics of glassy systems and elucidating the physical essence of the glassy state and glass transition. In this study, the microscopic dynamics of CuZr melts across the glass transition are investigated using molecular dynamics simulations. The single-particle dynamics in the supercooled CuZr melt is characterized by the random jump motions of atoms following long-term caging periods. To capture these dynamics, the displacement vector field is constructed based on the spatiotemporal distribution of these jump events. The simulation results reveal the presence of numerous vortex structures in the displacement vector field. Notably, the vortex formation rate, which is defined as the number of vortices generated per unit time, exhibits a sharp drop near the glass transition temperature. The probability distribution of vortex formation rates displays a bimodal pattern across the drop, indicating the coexistence of two distinct dynamical states associated with vortex formation. Multiple high-strain events are observed surrounding these vortices. It is found that the two vortex states across the transition exhibit markedly different characteristic ratios of vortices to high-strain events (1:4 vs 1:8), suggesting a change in the coupling strength between vortex formation and high-strain activity. The high-strain events predominantly form in the regions between positive and negative vortices, and the specific quantitative relationship between vortices and high-strain events indirectly reflects the presence of strongly interacting vortex-antivortex pairs in the melt. The abrupt doubling of the vortex-to-high-strain-event ratio during the vortex state transition implies that this transition is not merely a sudden change in vortex formation rate but also an enhancement of interactions between vortex-antivortex pairs, representing a change in global topological properties. These findings demonstrate that the vortex transition exhibits characteristics of a topological phase transition, thereby predicting the existence of a topological phase transition in the displacement vector field of metallic glass-forming systems. It is further speculated that vortices and high-strain events are associated with multiple secondary relaxation processes. This study provides a new perspective for understanding the dynamics of glass-forming systems and the glass transition.
下载: