Structural Evolution of Gold-Doped Bismuth Clusters AuBi\u3csub\u3e\u3ci\u3en\u3c/i\u3e\u3c/sub\u3e\u3csup\u3e–\u3c/sup\u3e (\u3ci\u3en\u3c/i\u3e = 4−8)

The structures of gold-doped bismuth clusters, AuBin− (n = 4−8), are investigated through a joint photoelectron spectroscopy and density functional theory (DFT) study. Well-resolved photoelectron spectra are obtained at several photon energies. Global minimum searches coupled with DFT calculations yield low-lying structures, whose relative energies are further evaluated by single-point energy calculations at the CCSD(T) level of theory. Vertical detachment energies are calculated with the inclusion of spin−orbit effects to compare with the experimental data. Three-dimensional structures are found to be dominant in this size range, while a planar low-lying isomer is observed only for AuBi4−. The AuBi6− cluster possesses a “bow-tie-like” global minimum structure. Major isomers of the other clusters studied here can all be viewed to possess this structural motif. The gold dopant favors increasingly higher coordination with bismuth in AuBin− (n = 4−8). Chemical bonding analyses are performed to understand the geometric and electronic structure evolution of these bimetallic clusters. The gold atom interacts with neighboring bismuth atoms via localized σ bonds at low-coordination sites but via delocalized σ bonds at high-coordination sites. Greater charge transfer from Bi to Au is found for higher-coordinated Au. Molecular dynamics simulations indicate that the assigned global minimum of AuBi7− is a highly stable structure, whereas the minor isomer of AuBi7− displays a fluxional behavior