| Abstract
| - Gold clusters with icosahedral, decahedral, and cuboctahedral shell structures, have been studied using theGupta many-body potential, to aid in the structural characterization of surface-deposited Au309 clusters usinghigh-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM). In this size regime,the calculations indicate that the icosahedral geometries are lower in energy than the decahedral andcuboctahedral structures but that the energy differences are small. This is consistent with the spread of differentgeometries observed by HAADF-STEM. Analysis of the different outlines and intensity profies of the HAADF-STEM images indicate that there are roughly equal numbers of decahedral and cuboctahedral clusters on thesurface. The unambiguous assignment of icosahedral geometries is more difficult because of the more-sphericalnature of these nanoparticles. Because the experimental uncertainty in the deposited cluster size is ±5%, agenetic algorithm has been used to search for the lowest energy isomers for AuN, clusters with N = 309 ±15 atoms. A variety of highly faceted structures have been found, many corresponding to incomplete ordistorted icosahedra, including a puckered icosahedral geometry for N = 309.
|
