| Abstract Scope |
Many properties of metallic glasses (deformation, diffusion, ageing, etc) originate from collective rearrangements of small groups of atoms called local structural excitations (LSEs). In a classical picture, shear loading would reduce LSE’s activation energy, which is analogous to the picture of dislocation migration in crystals, where the Peierls valley in potential energy landscape (PEL) is biased and tilted by external shear. However, the direct track of minimum energy pathways in PEL before and after shear loading by atomistic modeling shows only slight tilting, yielding an unreasonably small activation volume (10 times less than experiments). Here we show that, under external shear, the metallic glasses’ PEL topology is qualitatively changed. It becomes more fractal, where many tortuous pathways with large ratio of contour length and end-to-end length start to emerge. More importantly, those tortuous pathways have significantly lower activation barriers, which can naturally explain the enhanced LSEs’ activities estimated in experiments. |