Theoretical study on structures of small nonstoichiometric AlN clusters

Using the full-potential linear-muffin-tin-orbital molecular-dynamics method, we have performed calculations on the structures of nonstoichoimetric AlxNy (x+y=6-9) clusters. The lowest energy structures of these clusters are obtained. The stabilities and bond trends are discussed. For N-rich cluster, the structure is dominated by N-N bonds. For Al-rich cluster, it appears that, to have a N bonded only to Al atoms, its coordination needs to be at least three. The binding energy of the cluster increases as the size of cluster composition increases. The HOMO-LUMO gaps of these clusters have been evaluated.