The effect of sulfur covalent bonding on the electronic shells of silver clusters

The nature of the bonding in Ag(n)S(m)(0∕-) clusters, n = 1-7; m = 1-4, has been analyzed to understand its effect on the electronic shell structure of silver clusters. First-principle investigations reveal that the sulfur atoms prefer 2 or 3-coordinate sites around a silver core, and that the addition of sulfur makes the planar structures compact. Molecular orbital analysis finds that the 3p orbitals of sulfur form a bonding orbital and two weakly bonding lone pairs with silver. We examine the electronic shell structures of Ag6Sm, which are two electrons deficient of a spherical closed electronic shell prior to the addition of sulfur, and Ag7S(m)(-) clusters that contain closed electronic shells prior to the addition of sulfur. The Ag6S4 cluster has a distorted octahedral silver core and an open shell with a multiplicity of 3, while the Ag7S(n_(-) clusters have compact geometries with enhanced stability, confirming that the clusters maintain their electronic shell structure after bonding with sulfur.