冲击载荷下TATB晶体滑移和各向异性的分子动力学研究

采用ReaxFF反应力场和分子动力学方法,研究了1,3,5-三氨基-2,4,6-三硝基苯(TATB)炸药晶体在沿不同方向冲击载荷下的滑移和各向异性。冲击方向分别垂直于(101)、(111)、(011)、(110)、(010)、(100)和(001)晶面,冲击强度为10 GPa。研究结果表明,各冲击方向下可能被激发的滑移系均在{001}面,而其它滑移系均因很大的剪切阻力不容易被激发,这与TATB晶体沿c轴的层状结构和平面分子结构相符。预测了七个冲击方向下最容易被激发的滑移系,分别为(101)/{001}100、(111)/{001}010、(011)/{001}010、(110)/{001}010、(010)/{001}110、(100)/{001}120和(001)/{001}010。TATB晶体的冲击响应具有各向异性,动力学过程中体系的应力、能量、温度和化学反应都依赖于冲击方向。对垂直于(100)和(001)晶面的冲击,体系在滑移过程中遭遇的剪切阻力较高、持续时间较长,使得能量和温度较快升高,化学反应较容易发生;对垂直于(101)和(111)晶面的冲击,体系在滑移过程中遭遇的阻力较小且出现次数少,使得能量和温度缓慢升高,化学反应不易发生;对其余冲击方向,体系的响应居中。据此评价了7个冲击方向的相对敏感程度:(101)、(111)(011)、(110)、(010)(100)、(001)。本研究有助于在微观层次深入认识动载荷下TATB的响应机制、结构与性能的关系,为高能低感炸药的设计和研制提供理论参考。

The Slip and Anisotropy of TATB Crystal under Shock Loading via Molecular Dynamics Simulation

The slip and anisotropy of 2, 4, 6-triamino-1, 3, 5-trinitrobenzene (TATB) crystal under shock loading along various directions were investigated using molecular dynamics simulation combined with reactive force field (ReaxFF). The shock strength was approximately 10 GPa, and seven shock orientations normal to the (101), (111), (011), (110), (010), (100), and (001) crystal planes were considered. For these shock directions, the slip systems that are likely to be activated are predicted to be on the {001} plane, whereas others that could not be activated exhibit large shear stress barriers. These slip characteristics are consistent with the layered structure of TATB crystal along the c axis and the planar structure of TATB molecule. The most favorable slip systems are suggested to be (101)/{001}＜100＞, (111)/{001}＜010＞, (011)/{001}＜010＞, (110)/{001}＜010＞, (010)/{001}＜1$\bar 1$0＞, (100)/{001}＜120＞, and (001)/{001}＜010＞. TATB crystal exhibits anisotropic response to shock loading, that is, the shear stress, energy, temperature, and chemical reactivity during shear deformation depend on shock direction. For the (100) and (001) shock planes, the shear stress barrier is relatively high and lasts for a long time, leading to fast energy accumulation and temperature increment, which, in turn, increase the chemical reactivity. In contrast, for the (101) and (111) shock planes, the small shear stress barrier results in slow energy accumulation and temperature rise and, thus, low chemical reactivity. The (011), (110), and (010) shock planes exhibit intermediate responses. The sensitivity of the seven shock planes can be ranked as follows: (101), (111)＜(011), (110), (010)＜(100), (001). This study provides microscale insight into the response mechanisms and structure-property relationship of TATB crystal under dynamic loading and may facilitate designing explosives with high energy but low sensitivity.