Competition Among fcc-Like, Double-Layered Flat, Tubular Cage, and Close-Packed Structural Motifs for Medium-Sized Au<i>_n</i> (<i>n</i> = 21−28) Clusters

Using density functional theory calculations, we compared four kinds of possible structural motifs of the medium-sized Aun (n = 21−28) clusters, i.e., fcc-like, double-layered flat, tubular cage, and close-packed. Our results show strong competition between those structural motifs in the medium-sized gold clusters. Aun (n = 21−23) adopt fcc-like structure owing to the high stability of tetrahedral Au20. A structural transition from fcc-like to tubular occurs at Au24, and the tubular motif continues at Au27 and Au28. Meanwhile, a double-layered flat structure was found at Au25, and a pyramid-based structure at Au26. The relationship between electronic properties and cluster geometry was also discussed.