Structural Transitions from Pyramidal to Fused Planar to Tubular to Core/Shell Compact in Gold Clusters: Aun- (n = 21−25)

We report a joint theoretical and experimental study of low-lying structures and structural transitions of gold cluster anions Au n - in the size range of n = 21−25. Well-resolved photoelectron spectra are used to compare with density functional theory calculations and to identify the low-lying structures of the gold cluster anions. Due to the high stability of the tetrahedral Au 20, the pyramid-based structures are found to be competitive for n = 21−23. In addition to the pyramid-based structures, global-minimum searches also reveal two other generic structural types of low-lying clusters in the size range of n = 21−24, namely, the fused-planar and the hollow-tubular structures. At n = 24, the pyramid-based structures are no longer competitive and the hollow-tubular structures dominate the low-lying population. At n = 25, a structural transition from hollow-tubular to core/shell compact structure is observed.