Molecular dynamics calculations have been performed on a twohyphen;dimensional system of Lennardhyphen;Jones disks. Equilibrium thermodynamics data for 18 temperaturendash;density states of the system are presented and compared with values obtained from a simple Lennardhyphen;Jonesndash;Devonshire treatment. Three types of graphical displays of the data have been examined: ldquo;snapshotsrdquo; of the system configuration at some instant of time, motion pictures of the system dynamics created from sequences of snapshots, and plots of the trajectories of particle centers over various time intervals. The snapshots reveal the presence of relatively large vacancies in the spatial distribution of particles in the system, and the trajectory plots and motion pictures show that these vacancies may persist in the same region for times in excess of 10minus;12. The trajectory plots also indicate that cooperative motion is very important in the selfhyphen;diffusion process. The nature of the vacancies and the diffusive motion suggest a more than passive role of the attractive interparticle potential in determining the microstructure and microkinetics of the liquid state.
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