Theoretical Study of Small Scandium-Doped Silver Clusters ScAgn with n = 1-7: σ-Aromatic Feature

Geometry, chemical bonding, and aromatic feature of a series of small silver clusters doped by an Sc atom (ScAgn with n = 1-7) were investigated by means of density functional theory calculations. A planar shape is found for ScAgn including n from 4 to 7. The growth mechanism is established for the formation of the hexagonal and heptagonal metallic cycles following increase of the number of Ag atoms. Particularly, both clusters ScAg6- and ScAg7 present a planar cyclic form in which the Sc atom is situated at the central position of the Ag6 and Ag7 cycles. The σ aromaticity is unambiguously demonstrated by the existence of strongly diatropic current flows within the ring in both ScAg6- and ScAg7. The isovalent ScCu7 cluster has a similar ring current characteristic. In the Sc-doped ScAgn clusters, a delocalized bonding pattern is found as a connector between the dopant Sc and the Agn host, as indicated by an ELI_D analysis.