Molecular dynamics study on the effect of metal ion doping on the performance of HMX

In order to investigate the influence of metal ion-doped crystal defects on the performance of HMX, perfect models and defect models with different numbers of Zn²⁺, Na⁺, and Ca²⁺ dopants were established. Molecular dynamics simulations were conducted on ten models, and the bond length of the initiation bond, bond energy, cohesive energy density, and mechanical property parameters were analyzed. The results show that crystal defects lead to an increase in the initiation bond length of HMX explosive, with the Zn²⁺ doping model increasing by 2.8-4.45%, the Na⁺ doping model increasing by 2.23-3.78%, the Ca²⁺ doping model increasing by 2.49-3.03%, and the bond energy decreasing by 0.57-10.38%, which indicate an increase in the sensitivity of the defect models, a decrease in safety, and a deterioration of the stability of the explosive. The results also show that the cohesive energy density decreases with the increase in the number of dopants, with the most significant impact observed with Ca²⁺ ion doping, indicating that Ca²⁺ ion doping has the greatest influence on the sensitivity of HMX. Furthermore, crystal defects also result in a decrease in the tensile modulus, bulk modulus, and shear modulus of the HMX explosive, while increasing the Cauchy pressure and Poisson's ratio, indicating a decrease in rigidity and stiffness of the defect models, an increase in ductility, and a decrease in deformation resistance, thereby enhancing flexibility. The research results can provide a reference for subsequent analysis of the interaction between molecules and ions, as well as improving the safety of explosives.