Five fully optimized geometries of 3-nitro-1,2,4-triazol-5-one (NTO)/NH₃ and NTO/H₂O supermolecules have been obtained with density functional theory method at the B3LYP/6-311＋＋G** level. The intermolecular interaction energy was calculated with basis set superposition error correction and zero point energy correction. The greatest corrected intermolecular interaction energies of the NTO/NH₃ and NTO/H₂O supermolecules are －37.58 and －30.14 kJ/mol respectively, indicating that the intensity of interaction between NTO and NH₃ is stronger than between NTO and H₂O. Electrons in supermolecular systems transfer from NH₃ or H₂O to NTO. The strong hydrogen bonds contribute to the interaction energies dominantly. Natural bond orbital (NBO) analysis was performed to reveal the origin of the interaction. Based on the vibrational analysis, the changes of thermodynamic properties from the monomer to supermolecules with the temperature ranging from 200.0 to 800.0 K have been obtained using the statistical thermodynamic method. It was found that structures II and III can be produced spontaneously from NTO and NH₃ at room temperature, while structures IV, V and VI can only be produced spontaneously from NTO and H₂O at lower temperature.

Key words: 3-nitro-1,2,4-triazol-5-one, ammonia, water, intermolecular interaction, density functional theory, natural bond orbital analysis, thermodynamic property