Geometry optimization and harmonic vibrational frequency calculations have been carried out on various structures and low-lying, high- and low-spin electronic states of Al2N4 and AIN(n) clusters, where n = 4 to 7, at the B3LYP, MP2, and QCISD levels. The aim of these calculations was to search for states/structures that may be suitable candidates as precursors of high energy density materials. Well-bound charge-transfer states/structures with activated NN bonds were obtained. The exothermicities of the decomposition reactions of these states/structures to N-2 molecules were computed at up to the RCCSD(T)/aug-cc-pVQZ(no g) level of theory. The most exothermic decomposition reaction considered is AlN6 C-s Al.NN2N2N (N-6 ring), (4)A", (a')(1)(a')(1)(a")(1) --> Al + 3N(2). The calculated DeltaH(298K) is -226 kcal/mol, giving an energy release of over 75 kcal/mol per N-2 molecule. We conclude that AlNn systems are potential precursors of high energy density materials. In addition, the HOMOs of these states/structures have been examined in order to understand the stability of these states/structures. The ability of aluminum to introduce various degrees of covalency and ionicity to such clusters, which will stabilize the polynitrogen system, has been discussed.