Theoretical study of the structure of silver clusters

Neutral silver cluster isomers Ag-n (n=2 to 12) were studied by Kohn-Sham d ensity functional theory. There is a strong even-odd oscillation in cluster stability due to spin subshell closing. Nearest-neighbor interatomic dista nces do not evolve continuously from the diatomic (2.53 Angstrom) to the bu lk (2.89 Angstrom). After adding an empirical correction to the calculated values, we estimate that they are always near 2.68 Angstrom for 3 less than or equal ton less than or equal to6, and near 2.74 Angstrom for 7 less tha n or equal ton less than or equal to 12. We find several low-energy isomers at all cluster sizes larger than seven atoms with one exception: Ag-10 has a D-2d twinned pentagonal bipyramid isomer predicted to be 0.20 eV more st able than any other isomer. The ellipsoidal jellium model predicts rather w ell the shapes of stable silver clusters. Other models (extended Huckel, em pirical potential) fail to reproduce the energy ordering of cluster isomers . The structural attributes of low-energy silver cluster isomers Ag-n (n gr eater than or equal to7) are, in decreasing order of importance: a high mea n coordination; a shape that conforms to the ellipsoidal jellium model; and uniformity in atomic coordinations. (C) 2001 American Institute of Physics .