Sudden transition of dislocation dynamics in FCC crystals at ultralow temperatures

Abstract

Dislocation mobility, which is a fundamental unit of material plasticity, is determined by the predominant drag mechanism during dislocation motion. For edge dislocations in various FCC crystals, we first discover through a molecular dynamics simulation that the dislocation velocity abruptly changes at certain ultralow temperatures between 0.01 K and 10 K. We reveal that this sudden change is due to a change in the dislocation oscillation mode, and such a mode change is caused by the transition of the dislocation drag mechanism. Furthermore, we verify that the dislocation dynamics in FCC crystals at ultralow temperatures do not depend on material properties but are characterized by a fixed ratio of the dislocation frequency to the maximum frequency of the perfect lattice. Therefore, our findings indicate that the description of FCC crystal plasticity might be unifiable at ultralow temperatures independent of materials and suggest a possibility to further application to other materials.