Collect. Czech. Chem. Commun. 2007, 72, 185-196

On the Magic Character of Al6Au-

Michele L. Kimblea, Albert W. Castleman, Jr.a,*, Jose U. Revelesb and Shiv N. Khannab

a Departments of Chemistry and Physics, The Pennsylvania State University, University Park, PA 16802, U.S.A.
b Department of Physics, Virginia Commonwealth University, Richmond, VA 23284, U.S.A.


Joint experimental and theoretical studies have been carried out to identify the stability of aluminum gold clusters. The experimental studies where the AlnAu- clusters are generated via laser vaporization in a flow reactor and subsequently reacted with oxygen indicate that Al6Au- is an exceptionally stable species that is not only resistant to etching by oxygen but also grows in intensity when AlnAu- clusters are exposed to oxygen. Theoretical studies indicate that the six aluminum atoms in Al6Au- form an octahedron and that the Au atom occupies a hollow site above the triangular face of the octahedron. It is shown that it takes much larger energy to remove an Al or a Au atom compared to that for neighboring sizes, and this accounts for its resistance to oxygen. The special stability is rooted in the electronic spectrum that is marked by a large HOMO-LUMO gap of 1.38 eV, and the system is best described as a nearly free electron gas of 20 electrons.

Keywords: Gold aluminum clusters; Cluster stability; Cluster magic numbers; Laser vaporization; Oxidation; Mass spectrometry; Ab initio calculations.

References: 30 live references.