Anisotropic Shock Sensitivity of Cyclotrimethylene Trinitramine (RDX) from Compress-and-Shear Reactive Dynamics
Anisotropic Shock Sensitivity of Cyclotrimethylene Trinitramine (RDX) from Compress-and-Shear Reactive Dynamics
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DOI：
10.1021/jp300711m
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发表时间：
2012-05-10
影响因子：
3.7
通讯作者：
Goddard, William A., III
中科院分区：
文献类型：
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作者：
An, Qi;Liu, Yi;Goddard, William A., III
采用压剪反应动力学（CS-RD）模拟模型研究了环三亚甲基三硝胺（RDX）晶体的各向异性冲击波感度。我们预测，对于3和7 GPa之间的机械冲击，RDX是最敏感的冲击垂直于（100）和（210）平面，而它是不敏感的冲击垂直于（120），（111）和（110）平面。这些结果都与现有的实验信息一致，进一步验证了CS-RD模型区分敏感冲击方向和不敏感冲击方向的能力。我们发现，对于敏感的方向，冲击触发滑移系统，导致空间位阻产生大的剪切应力，导致增加的能量输入，增加温度，导致显着增加的化学反应。因此，我们的模拟表明，各向异性冲击敏感性的分子起源的结果从空间位阻剪切相邻滑移面在剪切变形。因此，应变能密度、温升和分子分解是区分各向异性敏感性的有效措施。我们应该强调的是，CS-RD已被开发为一种工具，用于快速（在几皮秒内）区分高能材料的敏感和不敏感冲击方向。如果这里使用的高应力和高速率持续更长的时间，并且对于更大的系统，它最终将导致所有方向的爆炸，但我们还没有证明这一点。
We applied the compress-and-shear reactive dynamics (CS-RD) simulation model to study the anisotropic shock sensitivity of cyclotrimethylene trinitramine (RDX) crystals. We predict that, for mechanical shocks between 3 and 7 GPa, RDX is most sensitive to shocks perpendicular to the (100) and (210) planes, whereas it is insensitive for shocks perpendicular to the (120), (111), and (110) planes. These results are all consistent with available experimental information, further validating the CS-RD model for distinguishing between sensitive and insensitive shock directions. We find that, for sensitive directions, the shock impact triggers a slip system that leads to large shear stresses arising from steric hindrance, causing increased energy inputs that increase the temperature, leading to dramatically increased chemical reactions. Thus, our simulations demonstrate that the molecular origin of anisotropic shock sensitivity results from steric hindrance toward shearing of adjacent slip planes during shear deformation. Thus, strain energy density, temperature rise, and molecule decomposition are effective measures to distinguish anisotropic sensitivities. We should emphasize that CS-RD has been developed as a tool to distinguish rapidly (within a few picoseconds) between sensitive and insensitive shock directions of energetic materials. If the high stresses and rates used here continued much longer and for larger systems, it would ultimately result in detonation for all directions, but we have not demonstrated this.