Origins of Stability in Mixed Bismuth−Indium Clusters

Abstract

The electronic structure and stability of neutral and negatively charged BixIny (x = 1−4, y = 1−6) clusters are investigated through anionic photoelectron spectroscopy employing magnetic bottle and photoelectron velocity map imaging experiments. Experimental and theoretical adiabatic and vertical detachment energies of the anionic species containing up to 4 Bi and 4 In atoms are deduced from first principles calculations. Among the BixIny series, many clusters are found to exhibit special stability in the mass spectra, exhibit a large gap between the highest occupied and lowest unoccupied molecular orbitals (HOMO−LUMO gap), and a large formation energy. This stability is rationalized by different mechanisms. Bi2In− is classified as a gas phase Zintl species despite only having three atoms, making it the smallest possible case. Bi3In2−, with 12 valence electrons and a closo structure in agreement with Wade’s rule, is similar to Bi3Ga2−, a gas phase Zintl analogue of Sn52−. Bi4In− and Bi4In2 are both found ...