Molecular dynamics study of the crystallisation of metastable fluids

Using the molecular dynamics technique we have investigated the mechanisms by which a metastable Lennard-Jones fluid transforms into a crystal and the morphology of the final state produced. The metastable states were created by equilibrating the fluid state at a temperature above the critical temperature then rapidly quenching to a temperature below the triple-point temperature. The starting densities were chosen so that the system was in the metastable two-phase region of the phase diagram after the quench. Three quite distinct starting densities were used corresponding to a low-density gas, a critical-density gas and a gas at a density of a typical liquid. For each of these starting conditions, the final state observed consists of crystalline and gaseous regions. However, the mechanism by which these states were reached and the morphology of the final state was quite distinct in the three cases studied.