Tetrazole monomers (I, II) and all of their possible stable dimers (1, 2, 3, 4, 5, 6, 7 and 8) were fully optimized by DFT method at the B3LYP/6-311++G** level. Among the eight dimers, there were two 1H-tetrazole dimers, three 2H-tetrazole dimers and three hetero dimers of 1H-tetrazole and 2H-tetrazole. Vibrational frequencies were calculated to ascertain that each structure was stable (no imaginary frequencies). The basis set superposition errors (BSSE) are 2.78, 2.28, 2.97, 2.75, 2.74, 2.18, 1.23 and 3.10 kJ/mol, and the zero point energy (ZPE) corrections for the interaction energies are 4.88, 4.18, 3.87, 3.65, 3.54, 3.22, 2.87 and 4.34 kJ/mol for 1, 2, 3, 4, 5, 6, 7 and 8, respectively. After BSSE and ZPE corrections, the greatest corrected intermolecular interaction energy of the dimers is –43.71 kJ/mol. The charge redistribution mainly occurs on the adjacent N–H…N atoms between submolecules. The charge transfer between two subsystems is very small. Natural bond orbital (NBO) analysis was performed to reveal the origin of the inter- action. Based on the statistical thermodynamic method, the standard thermodynamic functions, heat capacities (C0p), entropies (S0T) and thermal corrections to enthalpy (H0T), and the changes of ther- modynamic properties from monomer to dimer in the temperature range of 200.00 K to 700 K have been obtained. 1H-tetrazole monomer can spontaneously turn into two stable dimers at 298.15 K. Tetrazole monomers (I, II) and all of their possible stable dimers (1, 2, 3, 4, 5, 6, 7 and 8) were fully optimized by DFT method at the B3LYP / 6-311 ++ G ** level . Among the eight dimers, there were two 1H-tetrazole dimers, three 2H-tetrazole dimers and three hetero dimers of 1H-tetrazole and 2H-tetrazole. Vibrational frequencies were calculated to ascertain that each structure was stable (no imaginary frequencies). The basis set superposition errors (BSSE) are 2.78, 2.28, 2.97, 2.75, 2.74, 2.18, 1.23 and 3.10 kJ / mol and the zero point energy (ZPE) corrections for the interaction energies are 4.88, 4.18, 3.87, 3.65, 3.54 , 3.22, 2.87 and 4.34 kJ / mol for 1, 2, 3, 4, 5, 6, 7 and 8, respectively. After BSSE and ZPE corrections, the greatest corrected intermolecular interaction energy of the dimers is -43.71 kJ / mol. The charge redistribution mainly occurs on the adjacent N-H ... N atoms between submolecules. The charge transfer between two subsystems is very small. Natural bond orbital (NBO Based on the statistical thermodynamic method, the standard thermodynamic functions, heat capacities (COP), entropies (SOT) and thermal corrections to enthalpy (H0T), and the changes of ther - modynamic properties from monomer to dimer in the temperature range of 200.00 K to 700 K have been obtained. 1H-tetrazole monomer can spontaneously turn into two stable dimers at 298.15 K.