A theoretical prediction on the shear-induced phase transformation of TKX-50. Issue 46 (17th November 2017)

• Record Type: Journal Article
• Authors: Lu, Zhipeng; Xue, Xianggui; Zhang, Chaoyang
• Is Part Of: Physical chemistry chemical physics. Volume 19:Issue 46(2017)
• Page Start: 31054
• Page End: 31062
• Publication Date: 2017-11-17
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c7cp06363f
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : 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. Abstract : 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)/[101̄] with a space group of P 21 / 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 H δ + ⋯H δ + increases, which disfavors the proton transfer from NH3 OH + to C2 O 2 N8 2− 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.