Theoretical Study of Small Scandium-Doped Silver Clusters ScAg 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 (ScAg with n = 1-7) were investigated by means of density functional theory calculations. A planar shape is found for ScAg 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 ScAg and ScAg present a planar cyclic form in which the Sc atom is situated at the central position of the Ag and Ag cycles. The σ aromaticity is unambiguously demonstrated by the existence of strongly diatropic current flows within the ring in both ScAg and ScAg. The isovalent ScCu cluster has a similar ring current characteristic. In the Sc-doped ScAg clusters, a delocalized bonding pattern is found as a connector between the dopant Sc and the Ag host, as indicated by an ELI_D analysis.