Appearance of bulk-like motifs in Si, Ge, and Al clusters.

Using a genetic algorithm method to search for low-energy structures, we studied the evolution of structural motifs in Si, Ge, and Al clusters. We were able to observe how bulk-like structural motifs occur in these clusters as the size of the system increases, replacing structural motifs characteristic of clusters at smaller sizes. Si and Ge clusters adopt prolate structures at small sizes. While Si clusters switch to a spherical motif around the size of 30 atoms, Ge clusters exhibit plate-like motifs at the size of 40-atom clusters before transforming into more spherical shapes. For Al clusters, an ordered layered structural motif begins to appear at a relatively small cluster size around 25-27 atoms.