Stability of cationic silver doped gold clusters and the subshell-closed electronic configuration of AgAu.

Silver doping is a valuable route to modulate the structural, electronic, and optical properties of gold clusters. We combine photofragmentation experiments with density functional theory calculations to investigate the relative stability of cationic Ag doped Au clusters, AgAu (N ≤ 40). The mass spectra of the clusters after photofragmentation reveal marked drops in the intensity of AgAu , AgAu , and AgAu , indicating a higher relative stability of these sizes. This is confirmed by the calculated AgAu (N ≤ 17) dissociation energies peaking for AgAu , AgAu , and AgAu . While the stability of AgAu and AgAu can be explained by the accepted electronic shell model for metal clusters, density of states analysis shows that the geometry plays an important role in the higher relative stability of AgAu . For this size, there is a degeneracy lifting of the 1D shell, which opens a relatively large HOMO-LUMO gap with a subshell-closed 1S1P1P1D electronic configuration.