Dislocation nucleation induced by a shock wave in a perfect crystal: Molecular dynamics simulations and elastic calculations

We study the nucleation mechanism of the defects responsible for plastic flow in a $〈100〉$ fcc perfect single crystal submitted to a shock wave. In the large-scale nonequilibrium molecular dynamics simulation, small dislocation loops are created from thermal fluctuations just behind the shock front, in a narrow region of a few lattice parameters width. Their critical size is measured. The activation energy for the formation of an edge dipole, under high pressure, is computed within the Peierls framework. The elastic constants and the generalized stacking fault energy are computed from the interatomic potential. This model enables a qualitative discussion of the influence of material parameters such as intrinsic and unstable stacking faults versus elastic energy release.