The potential energy surfaces for the synthesis and decomposition reaction of N-8(C-s) --> N-5(+) + N-3(-) and isomerization reaction of N-8(C-s) to N-8(C-2h) were investigated by density functional theory (DFT). The species involved were fully optimized using four DFT methods. Relative energies were further calculated at the QCISD/6-311+G*//B3LYP/6-311+G* level. The barrier heights of Ns(Cs) --> N-5(+) + N-3(-) in forward and reverse directions were predicted to be 23.4 and 2.0 kcal/mol, respectively. Rate constants for the dissociation and synthesis pathways of Ns(Cs) were found by use of variational transition state theory. The barrier height for the isomerization reaction of Ns(Cs) to Ns(C2h) was predicted to be 4.0 kcal/mol at the QCISD/6-311+G*//B3LYP/6-311+G* level.