Theoretical investigation on properties of CL-20/HMX cocrystal explosive with crystal defect by molecular dynamics method

Crystal defect in energetic materials will directly affect its crystal structure and physicochemical properties, including mechanical sensitivity, thermal stability, mechanical properties, energetic performance, etc. In this article, the primitive and defective CL-20/HMX cocrystal models were established and the influence of crystal defects (including adulteration defect, dislocation defect and vacancy defect) on properties of CL-20/HMX cocrystal explosive was investigated by MD method. Results show that the trigger bond strength (N-N chemical bond) of CL-20 molecules in defective CL-20/HMX cocrystal models is lower than primitive cocrystal model and the mechanical sensitivity is increased. Compared with primitive cocrystal model, the binding energy between CL-20 and HMX molecules in defective models is decreased, meaning that the stability of defective models is weakened. The primitive cocrystal model has higher value of shear modulus, tensile modulus, and bulk modulus and lower value of Cauchy pressure than defective models, indicating that the rigidity and rupture strength of defective models are lowered. The density and detonation performance of defective CL-20/HMX cocrystal models are lower than primitive model, implying that the energy density is declined. Therefore, crystal defect can bring a negative influence on mechanical sensitivity, stability and energetic performance of CL-20/HMX cocrystal explosive, and the effect of vacancy crystal defect is more obvious and severe.