Molecular dynamics study of the solidification process in alkali halide cluster

Molecular dynamics (MD) simulations of the solidification process of an NaCl cluster are carried out. Voronoi analysis is employed to distinguish a crystal nucleus from molten NaCl. In the early stage of simulation, some small solid clusters of size smaller than the critical nucleus size are repeatedly formed and broken. Under the low-temperature condition (T = 700 K), in the later stage of the simulation, a polycrystal NaCl solid, in which two or three large solid grains survive, appears. Under the high-temperature condition (T = 740 K), one large single crystal cluster is formed. All simulations of this work are performed in a special-purpose computer for MD simulation, called MDGRAPE-2.