By means of constanthyphen;temperature, constanthyphen;pressure molecular dynamics techniques, we simulate the melting and crystallization processes of a model system composed of 864 Lennardhyphen;Jones (LJ) particles under periodic boundary conditions. On heating an fcc crystal of LJ particles, it is ascertained that melting takes place. On the other hand, a LJ liquid, when quenched slowly, crystallizes into a stacking of layers with stacking faults where each layer forms a closehyphen;packed structure with occasional point defects. The atomic configuration is not always nucleated into a completely ordered structure. A large hysteresis in the volumehyphen;temperature curve is observed. The volume contraction at the transition is characterized by two different growth rates, relatively slow at the first stage and relatively fast at the final stage. The critical cooling rate which separates the crystalhyphen;forming cooling rates and the glasshyphen;forming cooling rates is between 4times;1010and 4times;1011K/s for argon. On taking advantage of computer simulations, we analyze the microscopic atomic structure of our LJ system on the basis of the Voronoi and Delaunay tessellation.
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