Mechanical Anisotropy of the Energetic Crystal of 1,1-Diamino-2,2-dinitroethylene (FOX-7): A Study by Nanoindentation Experiments and Density Functional Theory Calculations

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• 作者：Xiaoqing Zhou ; Zhipeng Lu ; Qi Zhang ; Dong Chen ; Hongzhen Li ; Fude Nie ; Chaoyang Zhang
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：June 30, 2016
• 年：2016
• 卷：120
• 期：25
• 页码：13434-13442
• 全文大小：576K
• 年卷期：0
• ISSN：1932-7455

文摘

The mechanical anisotropy of the wavelike π-stacked energetic crystal of 1,1-diamino-2,2-dinitroethylene (FOX-7) is investigated by nanoindentation experiments and density functional theory (DFT) calculations. The FOX-7 crystal exhibits distinct mechanical anisotropy when indented on different faces. The elastic modulus and hardness of the (020), (−101), and (002) faces change in a decreasing order. The indentation on the (020) face induces the largest depth and the highest pile-up around all three edges of the indenter without causing crack formation. By contrast, the indentations on the (−101) and (002) faces are similar and induce a small indentation depth, low pile-up with a small distribution, and crack formation. Mechanical anisotropy is essentially determined by the wavelike π stacking of FOX-7 along the (020) face with the support of intermolecular hydrogen bonds; i.e., the molecular orientations and intermolecular spaces along different faces vary distinctly. This is also supported by the DFT calculations on uniaxial compression and shear sliding. In this work, the nature of the wavelike π stacking responsible for the low impact sensitivity of FOX-7 is discussed and compared with that of other explosives with different packing structures.