HMX晶体和HMX/F2311 PBXs力学性能的MD模拟研究

用分子动力学方法, 在295 K NVT系综和COMPASS力场下, 对环四甲撑四硝胺(HMX)晶体和F₂₃₁₁沿HMX (001), (010)和(100)晶面所构成PBXs模型的力学性能进行模拟研究. 结果表明, 加入F₂₃₁₁降低了HMX的刚性, 增强了它的延展性. 在HMX (100)面上添加F₂₃₁₁对提高体系的延展性较显著. 为考察温度对力学性能的影响及其机理, 在245～445 K范围完成对HMX (100)/F₂₃₁₁ PBX的MD模拟. 力学分析表明, 随温度增加HMX (100)/F₂₃₁₁的延展性呈抛物线变化规律, 归因于F₂₃₁₁分子链的运动及其构象随温度的变化.

MD Simulation Study on the Mechanical Properties of HMX Crystals and HMX/F2311 PBXs

Molecular simulation was applied to investigate the mechanical properties of β-octahydro- 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystals and the polymer-bonded explosives (PBXs) which were made from the HMX as a base and F₂₃₁₁ as a binder, in NVT ensemble using COM-PASS force field. The PBXs’ model was constituted by putting F₂₃₁₁ on crystal (001), (010) and (100) surface respectively. At 295 K, the elastic constants and the effective moduli were calculated by statistic analysis mode. Cauchy pressure C₁₂-C₄₄ was also calculated. It was shown that the rigidity was weakened and the ductibility was improved by adding small amount of F₂₃₁₁, and the ductibility improvement was most obvious when F₂₃₁₁ was put on HMX (100) crystal surface. From the temperature 245 to 445 K with the increase step of 50 K, pure HMX crystals and HMX (100)F₂₃₁₁ PBX were allowed to dynamically evolve. It is indi-cated that the mechanical properties of pure HMX crystals are unchanged because thermal effect of the volume is constrained by NVT ensemble. However, the ductibility of HMX (100)F₂₃₁₁ PBX changes according to a parabola with increasing temperature due to the improvement of F₂₃₁₁ chain moving ability and the simultaneous increment of high energy conformation ratio in this molecular chain, i.e., the increment of the molecular chain rigidity.