Molecular-dynamics simulation of rarefaction waves in media that can undergo phase transitions

The expansion of an instantly heated planar layer of condensed matter into a vacuum is investigated. It is shown that, as the result of a phase transition, a liquid shell characterized by a constant density and filled with matter in a two-phase state is formed in a rarefaction wave. By measuring the velocity of the shell and its density and mass, it is possible to obtain important information about the behavior of matter in the near-critical region of the phase diagram, where both experimental and theoretical investigations are complicated. Problems associated with the kinetics of the phase transition in rarefaction waves are investigated in detail. This investigation is based on a direct computer simulation of the dynamics of atoms and is free from any assumptions usually used in phenomenologically describing the fluctuation kinetics of the liquid-vapor transition.