Structures and stability of N 9 , N 9 − and N 9 + clusters

Ab initio molecular orbital calculations for N9, N−9 and N+9 isomers were carried out at the HF/ 6-31G*, B3PW91/6-31G*, B3LYP/6-31G* and MP2/ 6-31G* levels of theory. Stable equilibrium geometric structures were determined by harmonic vibrational frequency analyses at the HF/6-31G*, B3PW91/6-31G* and B3LYP/6-31G* levels of theory. The most stable free-radical N9 cluster is structure 1 with C2v symmetry and that of anion N−9 is structure 3 with Cs symmetry. Only one stable structure of the N+9 cation with C2v symmetry was predicted. Their potential application as high-energy-density materials has been examined.