Structure and stability for (AlN)+n and (AlN)-n (n=1-15) clusters

Using density functional theory (DFT) method with 6-31G* basis set, we have carried out the optimizing calculation of geometry, vibrational frequency and thermodynamical stability for (AlN)(n)(+) and (AlN)(n)(-) (n =1-15) clusters. Moreover, their ionic potential (IP) and electron affinity (EA) were discussed. The results show that the electrical charge condition of the cluster has a relatively great impact on the structure of the cluster and with the increase of n, this kind of impact is reduced gradually. There are no Al-Al and N-N bonds in the stable structure of (AlN)(n)(+) or (AlN)(n)(-), and the Al-N bond is the sole bond type. The magic number regularity of (AlN)(n)(+) and (AlN)(n)(-) is consistent with that for (AlN)(n), indicating that the structure with even n such as 2, 4, 6, ... is more stable. In addition, (AlN)(10) has the maximal ionization power (9.14 eV) and the minimal electron affinity energy (0.19 eV), which manifests that (AlN)(10) is more stable than other clusters.