Au60-: The Smallest Gold Cluster with the High-Symmetry Icosahedral Core Au13

Among coinage metal nanoclusters with 55 atoms, only Ag-55(-) and Cu-55(-) are the geometric magic-number clusters, as both exhibit icosahedral symmetry. Au-55(-), however, exhibits much lower symmetry due largely to the strong relativistic bonding effect. In this study, we collect a much larger population (>10,000 isomers) of low-energy isomers of Au-55(-) to Au-60(-) by using the combined density-functional theory and basin hopping global optimization method. We also include the spin-orbit effect in the density functional theory computation to achieve simulated photoelectron spectra in quantitative fashion. Remarkably, we uncover that the Au-13, core with the highest icosahedral (I-h) symmetry emerges at the size of Au-60(-). Stability analysis suggests that Au-57(-) with 58 valence electrons, an electronic magic number, is the relatively more stable cluster in the size range considered. Overall, in this size range we reveal a compromise between the trend toward having a perfect icosahedral 13-atom core and the strong relativistic bonding effect.