Molecular dynamics simulations for pure ε-CL-20 and ε-CL-20-based PBXs

Molecular dynamics has been employed to simulate the well-known high energy density compound ε-CL-20 (hexanitrohexaazaisowurtzitane) crystal and 12 ε-CL-20-based PBXs (polymer bonded explosives) with four kinds of typical fluorine polymers, i.e., polyvinylidenedifluoride, polychlorotrifluoroethylene, fluorine rubber (F₂₃₁₁), and fluorine resin (F₂₃₁₄) individually. The elastic coefficients, isotropic mechanical properties (tensile moduli, bulk moduli, shear moduli, and poission's ratios), and bonding energy are first reported for ε-CL-20 crystal and ε-CL-20-based polymer bonded explosives (PBXs). The mechanical properties of ε-CL-20 can be effectively improved by blending with a small amount of fluorine polymers, and the whole effect of the adding fluorine polymers to improve mechanical properties of PBXs along the three crystalline surfaces of ε-CL-20 is found to be (100) ≈ (001) > (010). The interaction between each of the crystalline surfaces and each of the fluorine polymers is different, and the ordering of binding energy for the three surfaces is (001) > (100) > (010); F₂₃₁₄ always has the strongest binding ability with the three different surfaces. F₂₃₁₄ can best improve the ductibility and tenacity of PBX when it is positioned on ε-CL-20 (001) crystal surface. The calculations on' detonation performances for pure ε-CL-20 crystal and the four ε-CL-20-based PBXs show that adding a small amount of fluorine polymer into pure ε-CL-20 will lower detonation performance, but each detonation parameter of the obtained PBXs is still excellent.