A theoretical prediction on the shear-induced phase transformation of TKX-50.
A theoretical prediction on the shear-induced phase transformation of TKX-50.
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DOI：
10.1039/c7cp06363f
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发表时间：
2017-11
期刊：
影响因子：
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通讯作者：
Zhipeng Lu;Xianggui Xue;Chaoyang Zhang
中科院分区：
文献类型：
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作者：
Zhipeng Lu;Xianggui Xue;Chaoyang Zhang
5，5 '-双四唑-1，1'-二醇二羟铵（TKX-50）是一种新型的含能材料，由于其优异的性能，其性能优于许多常用炸药，是一种很有前途的替代炸药。然而，关于它的物理化学性质，特别是它在外部刺激下完全衰变的潜在机制的知识仍然很少。在本研究中，我们确定了（010）/[101]的优先滑移系和TKX-50的剪切诱导相变的理论计算的帮助下。换句话说，观察到通过沿着（010）/[101]或（010）/[101[结合macron]]的滑移系剪切TKX-50而形成TKX-50的新相γ-TKX-50，所述滑移系具有P21/a的空间群、9.4 kcal mol-1的升高能量和相对于原始TKX-50膨胀4%的晶胞。此外，沿沿着（010）/[101]剪切TKX-50最容易形成γ-TKX-50，其最低能垒为18.6 kcal mol-1，远低于TKX-50衰变的能垒。γ-TKX-50的预测弹性常数验证了其机械稳定性，相对于原始TKX-50具有降低的机械各向异性。此外，相变后氢键减弱，Hδ+Hδ+的静电排斥作用增强，不利于质子从NH3 OH+向C2 O2 N82-的转移，不利于TKX-50的热衰变.这表明剪切诱导的从TKX-50到γ-TKX-50的转变可以通过提高质子转移的能垒来增强热稳定性，这可能导致TKX-50的机械灵敏度较低。希望本研究能丰富对TKX-50对抗外界热机械刺激的潜在机制的了解。此外，结合新发现的热诱导相、本研究中观察到的剪切诱导相和原始相，TKX-50至少有三个相。
Dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) is a new and attractive energetic material that outperforms numerous common explosives because of its excellent properties and performance, and is thus a promising candidate to replace some of them. Nevertheless, knowledge of its physico-chemical properties, in particular, the underlying mechanism for it undergoing external stimuli for complete decay still remains poor. In the present study, we ascertain a preferred slip system of (010)/[101] and a shear-induced phase transition of TKX-50 with the aid of theoretical calculations. In other words, a new phase of TKX-50, γ-TKX-50, is observed to be formed by shearing TKX-50 along a slip system of (010)/[101] or (010)/[101[combining macron]] with a space group of P21/a, elevated energy of 9.4 kcal mol-1 and a unit cell expanded 4%, relative to the original TKX-50. Moreover, γ-TKX-50 can most readily be formed by shearing TKX-50 along (010)/[101] with a lowest energy barrier of 18.6 kcal mol-1, which is much below that for TKX-50 decay. The predicted elastic constants of γ-TKX-50 verify its mechanical stability with decreased mechanical anisotropy relative to the original TKX-50. In addition, we find that, after phase transition, the hydrogen bonding is weakened, while the electrostatic repulsion of Hδ+Hδ+ increases, which disfavors the proton transfer from NH3OH+ to C2O2N82- to facilitate the thermal decay of TKX-50. This suggests that the shear-induced transition from TKX-50 to γ-TKX-50 can enhance thermal stability by elevating the energy barrier for proton transfer, potentially contributing to the low mechanical sensitivity of TKX-50. Hopefully, this study would enrich the insight into the underlying mechanism of TKX-50 against external thermal-mechanical stimuli. Moreover, in combination with the newly found heat-induced phase, the shear-induced phase observed in the present study and the original one, there are at least three phases for TKX-50.