Polynitrogen compounds, are rare molecules having only nitrogen atoms. In recent years, they have been considered as promising candidates of clean (green) high energy density materials. They possess high energy content and their sole decomposition product is N-2. Presently some prismatic polynitrogen structures (N-6 - N-14) are considered within the limitations of density functional theory at the levels of B3LYP/6-311++G(d,p) and B3LYP/cc-PVTZ. The calculations reveal that they are all highly endothermic but stable. Certain quantum chemical properties, IR and UV/Vis spectra are reported. Homolytic bond cleavage of top rings are considered. Then, the transition state and activation energies, and also homolytic bond dissociation energies for the top rings have been calculated at the level of UB3LYP/6-311++G(d,p). Also NICS(0) values have been calculated at the level of B3LYP/6-311++G(d,p). The results indicate that N-6 and N-10 have aromatic and nonaromatic top (and also base) rings, respectively. All the rest of the structures have antiaromatic rings (all the structures have antiaromatic N-4 rings).