  Classical molecular dynamics simulation with embedded atom method potential
had been performed to investigate the surface structure and solidification
morphology of aluminum nanoclusters Aln (n = 256, 604, 1220 and 2048). It is
found that Al cluster surfaces are comprised of (111) and (001) crystal planes.
(110) crystal plane is not found on Al cluster surfaces in our simulation. On
the surfaces of smaller Al clusters (n = 256 and 604), (111) crystal planes are
dominant. On larger Al clusters (n = 1220 and 2048), (111) planes are still
dominant but (001) planes can not be neglected. Atomic density on cluster
(111)/(001) surface is smaller/larger than the corresponding value on bulk
surface. Computational analysis on total surface area and surface energies
indicates that the total surface energy of an ideal Al nanocluster has the
minimum value when (001) planes occupy 25% of the total surface area. We
predict that a melted Al cluster will be a truncated octahedron after
equilibrium solidification.
