Theoretical calculation into the effect of molar ratio on the structures, stability, mechanical properties and detonation performance of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane/ 1,3,5-trinitro-1,3,5-triazacyco-hexane cocrystal

Molecular dynamics (MD) simulation was conducted to research the effect of molar ratio on the thermal stability, mechanical properties, and detonation performance of HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane)/RDX (1,3,5-trinitro-1,3,5-triazacyco-hexane) cocrystal explosive at ambient condition. The binding energy, mechanical properties, and the detonation parameters of the pure β -HMX, RDX crystal, and the cocrystal models were got and contrasted. The results demonstrate that molar ratio has a great influence on the properties of the cocrystal system. The binding energy of the cocrystals has the maximum values at the 1:1 molar ratio, indicating that the stability of HMX/RDX(1:1) cocrystal is the best and HMX and RDX may prefer to cocrystallizing at 1:1 molar ratio. What’s more, the tensile modulus (E) and shear modulus (G) of the HMX/RDX(1:1) cocrystals have the minimum value, while the C 12 – C 44 and K/G have the maximum value, implying that the cocrystal at 1:1 molar ratio has the best mechanical properties. Simultaneously, the E, K, and G of the cocrystals are all smaller than those of β -HMX’s and generally larger than those RDX’s, while the Cauchy pressure ( C 12 – C 44 ) and K/G ratio were greater, demonstrating that cocrystallizing can improve the brittleness and enhance the ductility. The detonation velocity ( D ) and detonation pressure ( P ) decrease with the rising RDX content, while the properties are still superior to the pure RDX crystal; thus, the energy properties of the cocrystal are still excellent. In a word, HMX/RDX cocrystal at 1:1 molar ratio has the best thermal stability, mechanical properties, and the excellent energetic performance.