The electronic structure calculations locate the local minima for bicyclic N-10 and the fullerene analog N-60, both as high-energy density species. The bridging N-N bond in N-10 is quite remarkably strong (DeltaE [N-10 --> 2N(5)] = 93 kcal/ mol), yet flexible to allow a facile rotation of one ring with respect to the other. This property could permit Nio to serve as a building block for specific clustering into the nitrogen buckminsterfullerene structure.