On the remarkable resistance to oxidation by the Bi cluster.

The reactivity of Bi clusters ( = 2 to 30) with O is found to display even-odd alternations. The open-shell even-sized Bi clusters are more reactive than the closed-shell odd-sized clusters, except Bi, which exhibits no observable reactivity toward O. We have investigated the structure and bonding of Bi to understand its remarkable resistance to oxidation. We find that the most stable structure of Bi consists of two Bi cages linked by a Bi dimer, where each atom is bonded to three neighboring atoms. Chemical bonding analyses reveal that each Bi uses its three 6 electrons to form three covalent bonds with its neighbors, resulting in a Bi cluster without any dangling bonds. We find that the robust Bi framework along with the totally delocalized unpaired electron is responsible for the surprising inertness of Bi toward O. The Bi framework is similar to that in Hittorf's phosphorus, suggesting the possibility to create bismuth nanoclusters with interesting structures and properties.