Theoretical investigation to predict properties of CL-20/HMX cocrystal explosive with adulteration crystal defect: a molecular dynamics (MD) study

To explore the effects of adulteration crystal defect on performances of hexanitrohexaazaisowurtzitane/octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (CL-20/HMX) cocrystal explosive, the CL-20/HMX cocrystal model was established based on its lattice parameters. Besides, defective CL-20/HMX cocrystal models with adulteration ratios of 1.85%, 3.70%, 5.56%, 7.41%, and 9.26% were also established, respectively. Molecular dynamics (MD) method was selected to optimize the crystal structure and predict performances of each model. The correlated energies and parameters, including binding energy, trigger bond rupture energy, cohesive energy density (CED), and detonation parameters were calculated and compared. Results show that binding energy in defective CL-20/HMX models is decreased by 12.02-307.05 kJ/mol, implying that the intermolecular interaction energy between CL-20 and HMX molecules is decreased and stability is weakened. Adulteration crystal defect makes the trigger bond rupture energy and CED decreased by 1.06-22.04 kJ/mol and 0.003-0.122 kJ/cm3 respectively, indicating that the sensitivity of defective models is increased and safety is worsened. The crystal density of defective cocrystal models is decreased by 0.005-0.142 g/cm3, detonation velocity is decreased by 53-508 m/s, and detonation pressure is decreased by 0.52-5.09 GPa, meaning that defective cocrystal models have lower energy density than that of primitive model. Hence, adulteration crystal defect will bring passive influence on stability, safety and energetic performance of CL-20/HMX cocrystal explosive.