Ge Ni-Na, Wei Yong-Kai, Song Zhen-Fei, Chen Xiang-Rong, Ji Guang-Fu, Zhao Feng, Wei Dong-Qing
National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, Chinese Academy of Engineering Physics , Mianyang 621999, China.
J Phys Chem B. 2014 Jul 24;118(29):8691-9. doi: 10.1021/jp502432g. Epub 2014 Jul 1.
Molecular dynamics simulations in conjunction with multiscale shock technique (MSST) are performed to study the initial chemical processes and the anisotropy of shock sensitivity of the condensed-phase HMX under shock loadings applied along the a, b, and c lattice vectors. A self-consistent charge density-functional tight-binding (SCC-DFTB) method was employed. Our results show that there is a difference between lattice vector a (or c) and lattice vector b in the response to a shock wave velocity of 11 km/s, which is investigated through reaction temperature and relative sliding rate between adjacent slipping planes. The response along lattice vectors a and c are similar to each other, whose reaction temperature is up to 7000 K, but quite different along lattice vector b, whose reaction temperature is only up to 4000 K. When compared with shock wave propagation along the lattice vectors a (18 Å/ps) and c (21 Å/ps), the relative sliding rate between adjacent slipping planes along lattice vector b is only 0.2 Å/ps. Thus, the small relative sliding rate between adjacent slipping planes results in the temperature and energy under shock loading increasing at a slower rate, which is the main reason leading to less sensitivity under shock wave compression along lattice vector b. In addition, the C-H bond dissociation is the primary pathway for HMX decomposition in early stages under high shock loading from various directions. Compared with the observation for shock velocities V(imp) = 10 and 11 km/s, the homolytic cleavage of N-NO2 bond was obviously suppressed with increasing pressure.
结合多尺度冲击技术（MSST）进行分子动力学模拟，以研究沿a、b和c晶格向量施加冲击载荷时凝聚相HMX的初始化学过程和冲击敏感性的各向异性。采用了自洽电荷密度泛函紧束缚（SCC-DFTB）方法。我们的结果表明，在11 km/s的冲击波速度响应中，晶格向量a（或c）与晶格向量b存在差异，这是通过反应温度和相邻滑移面之间的相对滑动速率来研究的。沿晶格向量a和c的响应彼此相似，其反应温度高达7000 K，但沿晶格向量b则有很大不同，其反应温度仅高达4000 K。与沿晶格向量a（18 Å/ps）和c（21 Å/ps）的冲击波传播相比，沿晶格向量b的相邻滑移面之间的相对滑动速率仅为0.2 Å/ps。因此，相邻滑移面之间较小的相对滑动速率导致冲击载荷下的温度和能量以较慢的速率增加，这是导致沿晶格向量b在冲击波压缩下敏感性较低的主要原因。此外，在来自各个方向的高冲击载荷下，早期HMX分解的主要途径是C-H键断裂。与冲击速度V(imp)=10和11 km/s的观测结果相比，随着压力增加，N-NO2键的均裂明显受到抑制。
