Evolution of unsupported shocks in a two-dimensional Yukawa solid

Molecular dynamical simulations are performed to investigate the evolution of unsupported shocks in a two-dimensional Yukawa solid. When a boundary of the solid moves uniformly inward, a compressional shock is generated with a propagating front. An unsupported shock forms if the moving boundary suddenly stops, and a rarefaction wave (RW) is generated near this boundary. The original shock front propagates more slowly than the head of the new RW; as a result, the shock front is eventually overtaken by the RW and a new front appears. It is found that the speed of this new front can be expressed as the average of the previous shock front speed and the longitudinal sound speed, the latter of which has a transition depending on the initial compressional speed of the moving boundary. It appears that this transition of the new shock front speed probably can be attributed to change of the compressibility properties.