EVOLUTION OF BONDING IN ALNN CLUSTERS - A TRANSITION FROM NONMETALLICTO METALLIC CHARACTER

The evolution of the equilibrium geometry, binding energy, and electro nic structure of AlnN clusters has been studied using first-principles calculations based on density-functional theory. The bonding in small (n less than or equal to 6) AlnN clusters, in analogy with the electr onic structure of bulk aluminum nitride, is found to be intermediate b etween ionic and covalent. However, the electronic structure takes on a metallic character in Al12N and the cluster's chemistry is seen to m imic the chemistry of an alkali atom. The calculations also reveal the existence of an anomalously stable Al3N cluster, in sharp contrast wi th the bulk stoichiometric composition. [S0163-1829(98)00804-2].