Abstract: The existence of cluster N 8 was predicted according to the existence of N 5＋and N 3－ ．TwentyN 8 isomers were then designed by using the molecular simulation software．The full geometry optimiza-tion‚thermodynamics calculation and harmonic vibration frequency analysis of these twenty N 8molecules were performed at the HF／STO-3G level with the ab initio method of quantum chemistry．The synthesis routes of N 8 in experiments were finally discussed．The calculated results show that twelve of the twenty N 8 isomers can stably exit‚and that the planar double five-member ring form of N 8 with D 2h symmetry is the most stable．Energy analysis result indicates that a N 8 molecule with a stable structurecontains much higher energy than four N 2 molecules‚which means N 8 is a potential green material with high energy density．

Key words: cluster N₈, molecular model design, ab initio calculation, isomer, high energy density material