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Nine single-bonded nitrogen cluster-type molecules N x s 8᎐24 were x investigated using the B3LYPr6-31G** DFT method. Geometrical optimization, vibrational frequencies, and thermal chemical calculation of these molecules were compared. All the molecules were proved to be local minima. The coordination number three of all atoms and bond distances at around 1.5 A indicate that all the molecules were Ž . constructed with single bonds. A comparison of the average bond energy BE s ⌬ H rn , a B Ž . Ž Ž . . single-bond-type delocalization energy DErn , enthalpy of formation ⌬ H r xr2 , B f 12 6 h 8 h compact structures are the most important factors for the single-bonded cluster-type molecule formation. The four-or six-membered ring structures do not favor this type of molecule.