D.E. BERGERON/P.J. ROACH/A.W. CASTLEMAN/N.O. JONES/S.N.KHANNA

Scientists have discovered that clusters of aluminum atoms impersonate different elements, depending on how many atoms make up the group. Findings published today in the journal Science suggest that the clusters could be tailored to achieve desirable properties, such as conductivity.

Shiv N. Khanna of Virginia Commonwealth University and his colleagues analyzed the geometry, electronic structure and chemical properties of bunches of 13 and 14 aluminum atoms. They also tested the groupings experimentally by reacting them with iodine atoms. The results show that a cluster of 13 behaves much like a single atom of iodine does, whereas a cluster of 14 exhibited different behavior, acting more like an alkaline earth atom, such as beryllium. Further reactivity studies indicate that the new class of so-called polyiodides can be highly stable in nature because of their electronic properties, which include bonds that are different than those found in individual atoms. "The discovery of these new iodine compounds, which include aluminum clusters, is critical because it reveals a new form of 'superatom' chemistry," Khanna remarks. "In the future, we may apply this chemistry, building on our previous knowledge, to create new materials for energy applications and even medical devices."

Indeed, the new aluminum assemblages could add a new dimension to the periodic table and provide chemists with novel potential building blocks. Notes Khanna: "Assembling Al₁₃I units may provide aluminum materials that will not oxidize, and may help to overcome a major problem in fuels that burn aluminum particles."