Theoretical study of the structure of silver clusters

Neutral silver cluster isomers Agn (n=2 to 12) were studied by Kohn–Sham density functional theory. There is a strong even-odd oscillation in cluster stability due to spin subshell closing. Nearest-neighbor interatomic distances do not evolve continuously from the diatomic (2.53 Å) to the bulk (2.89 Å). After adding an empirical correction to the calculated values, we estimate that they are always near 2.68 Å for 3⩽n⩽6, and near 2.74 Å for 7⩽n⩽12. We find several low-energy isomers at all cluster sizes larger than seven atoms with one exception: Ag10 has a D2d twinned pentagonal bipyramid isomer predicted to be 0.20 eV more stable than any other isomer. The ellipsoidal jellium model predicts rather well the shapes of stable silver clusters. Other models (extended Hückel, empirical potential) fail to reproduce the energy ordering of cluster isomers. The structural attributes of low-energy silver cluster isomers Agn (n⩾7) are, in decreasing order of importance: a high mean coordination; a shape that conforms to the ellipsoidal jellium model; and uniformity in atomic coordinations.