Argon cluster evaporation dynamics

Abstract

Expansion of argon clusters in a vacuum is simulated via molecular dynamics computations. The resulting evaporation dynamics is investigated with observations of temperature and pV energy loss curves. Observed cooling curves (T vs n) and collapse curves (pV/n vs n) are found to depend on final cluster size but not the initial cluster ensemble. The evaporation mechanism consists of an initial rapid cooling-and-collapse stage of a preliquid dense-gas-like cluster, followed by ‘‘equilibrium’’ evaporation, and then another cooling stage of the resulting relatively incompressible liquidlike subcluster. Elements of this dynamics evaporation mechanism are tested by examination of finite n phase diagrams constructed using Metropolis Monte Carlo simulations of the fixed T and p ensemble.