3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide (LAX-112) is one of the early used insensitive tetrazine explosives with its nitrogen content,enthalpy of formation,density,critical diameter of 58.3%,+164 kJ·mol-1,1.834 g·cm-3,and less than 6 mm,respectively.Its detonation velocity and detonation pressure are 8.26kmS-1 and 24.2GPa respectively [1-3].In this paper,we theoretically investigated the intermolecular interaction and thermodynamic properties of LAX-112 dimers.Three fully optimized structures of 3,6-diamino-1,2,4,5-tetrazine-1,4-di-oxide (LAX-112) dimers have been obtained with the density functional theory (DFT) method at B3LYP/6-311++G** level.Vibrational frequency calculation was carried out to ascertain that each structure is the stable one (no imaginary frequencies).The intermolecular interaction energy is calculated with basis set superposition error (BSSE) correction and zero point energy (ZPE) correction.The greatest corrected binding energy among the three dimers is -42.38 kJ·mol-1.The charge redistribution mainly occurs on the adjacent O(N)……H atoms between submolecules and the charge transfer between two subsystems is very small.Natural bond orbital (NBO) analysis was performed to reveal the origin of the interaction.Based on the vibrational analysis,the standard thermodynamic functions (heat capacities (Cθ p),entropies (Sθ m) and enthalpies (Hθm)) and the changes of thermodynamic properties from the monomer to dimer with the temperature ranging from 200.00 K to 800.00 K have been obtained using the statistical thermodynamic method.The results show that the strong hydrogen bonds dominantly contribute to the dimers,while the bonding energies are not only determined by the hydrogen bonding.The dimerization process of dimer Ⅱ can occur spontaneously at room temperature.