Atomistic Simulations of the Motion of an Edge Dislocation in Aluminum Using the Embedded Atom Method

The motion of an edge dislocation is analyzed for temperatures ranging from 10 K to 200 K and for stresses up to 5 GPa. The dislocation velocity versus the applied shear stress curve can be divided into four regimes corresponding to successively higher shear stresses. In the first regime, the applied shear stress is below the Peierls stress and the dislocation velocity is nominally zero. In the second regime, the dislocation velocity decreases with increasing temperature indicating the presence of a drag due to thermal phonons. In the third regime, the dislocation reaches a sub-sonic limiting velocity that can be predicted by a two-dimensional lattice-dynamics analysis. Such an analysis predicts a limiting velocity for a moving defect when the phase velocity and the group velocity are equal. If even higher shear stresses are applied, the dislocation travels with a transonic velocity of √2 times the shear wave speed.