Observation of the solid and liquid separation after the shock propagation in a two-dimensional Yukawa solid

Abstract

After the propagation of compressional shocks in a two-dimensional (2D) Yukawa solid, the structure and dynamics of the postshock region are investigated using molecular dynamical simulations. When the compressional speed is significantly higher than 0.354a0ωpd, the postshock region melts completely; however, when this compressional speed is much lower than 0.283a0ωpd, the postshock region is still in the solid state. It is found that, when the compressional speed 0.283a0ωpd≤vleft≤0.354a0ωpd, from the calculated Voronoi diagram, the postshock region clearly exhibits the coexistence of the solid close to the compressional boundary and the liquid in the other part. The calculated averaged kinetic temperature profile in the postshock region exhibits a roughly linear increase in front of the compressional boundary, and the spatial portion whose averaged kinetic temperature is lower than the melting point agrees with the solid region determined directly from the Voronoi diagram. This spatial variation trend of the averaged kinetic temperature in the postshock region is attributed to the dynamical heterogeneity of the 2D Yukawa systems, which is more severe when the mean kinetic temperature is around the melting point. Test runs with various conditions further confirm this interpretation.