High-Pressure Structural Response of an Insensitive Energetic Crystal: 1,1-Diamino-2,2-dinitroethene (FOX-7)

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• 作者：Zbigniew A. Dreger ; Adam I. Stash ; Zhi-Gang Yu ; Yu-Sheng Chen ; Yuchuan Tao ; Yogendra M. Gupta
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：December 8, 2016
• 年：2016
• 卷：120
• 期：48
• 页码：27600-27607
• 全文大小：494K
• ISSN：1932-7455

文摘

High-pressure structural response of an insensitive energetic crystal—1,1-diamino-2,2-dinitroethene (FOX-7)—was examined to gain insight into its structural and chemical stability and to obtain isothermal compression data. Using synchrotron single-crystal X-ray diffraction measurements, details of pressure-induced structural changes to 12.8 GPa were determined across three FOX-7 phases: α (P2₁/n), α′ (P2₁/n), and ε (P1). We found that the C–NO₂ bond is the most compressible chemical bond, and high pressure significantly reduces and homogenizes the length of H bonds in the hydrogen-bond network. The α′−ε phase transition, at 4.5 GPa, significantly affects all molecular and crystal properties, whereas the α–α′ transition, at 2 GPa, is associated with subtle molecular and intermolecular changes. Anisotropic compressibility was observed over the entire pressure range, consistent with the layered structure of the crystal. The equation-of-state parameters were obtained using the third-order Birch–Murnaghan equation below and above the α′−ε phase transition. It is shown that dispersion-corrected DFT-D calculations reproduce well pressure-induced changes in the unit cell parameters. The findings of this work provide new insights into the molecular and structural mechanisms governing the high-pressure stability/insensitivity of insensitive energetic crystals.