A theoretical prediction on the shear-induced phase transformation of TKX-50

作者：Lu, Zhipeng; Xue, Xianggui; Zhang, Chaoyang^*

来源：Physical Chemistry Chemical Physics, 2017, 19(46): 31054-31062.

DOI：10.1039/c7cp06363f

• PENTAERYTHRITOL TETRANITRATE
• THERMAL-DECOMPOSITION
• CRYSTAL ORIENTATION
• ENERGETIC CRYSTAL
• SENSITIVITY
• PRESSURE
• IMPACT
• TEMPERATURE
• STABILITY
• BEHAVIOR

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 physicochemical 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, gamma-TKX-50, is observed to be formed by shearing TKX-50 along a slip system of (010)/[101] or (010)/[10 (1) over bar] with a space group of P2(1)/a, elevated energy of 9.4 kcal mol(-1) and a unit cell expanded 4%, relative to the original TKX-50. Moreover, gamma-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 gamma-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 H delta+center dot center dot center dot H delta+ increases, which disfavors the proton transfer from NH3OH+ to (C2ON82-)-N-2 to facilitate the thermal decay of TKX-50. This suggests that the shear-induced transition from TKX-50 to gamma-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.

• 出版日期2017-12-14
• 单位中国工程物理研究院; 北京计算科学研究中心