Song Liang, Zhao Feng-Qi, Xu Si-Yu, Ju Xue-Hai, Ye Cai-Chao
Key Laboratory of Soft Chemistry and Functional Materials of MOE, School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China.
Science and Technology on Combustion and Explosion Laboratory, Xi'an Modern Chemistry Research Institute, Xi'an, 710065, China.
Sci Rep. 2020 Feb 11;10(1):2317. doi: 10.1038/s41598-020-59261-3.
Temperature-induced morphological changes are one of the strategies for designing crystal shapes, but the role of temperature in enhancing or inhibiting crystal growth is not well understood yet. To meet the requirements of high density and low sensitivity, we need to control the crystal morphology of the energetic materials. We studied the crystal morphology of 1,1-diamino-2,2-dinitroethylene (FOX-7) in dimethyl sulfoxide/water mixed solvent by using the modified Hartman-Perdok theorem. Molecular dynamics simulations were used to determine the interaction of FOX-7 and solvents. The results showed that the crystal shape of FOX-7 is hexagonal, the (101) face is the largest exposed face and is adjacent to six crystal faces at 354 K. As the temperature goes down, the area of the (001) face is significantly reduced. The crystal morphology of FOX-7 at 324 K has a smaller aspect ratio of 4.72, and this temperature is suitable for tuning the morphology from slender hexagon into diamond. The prediction results are in remarkable agreement with the experiments. Moreover, we predicted the evolution path of FOX-7 morphology by Gibbs-Curie-Wulff theorem and explained the variation of crystal shape caused by different external conditions in the actual crystallization process.
温度诱导的形态变化是设计晶体形状的策略之一，但温度在促进或抑制晶体生长中的作用尚未得到充分理解。为满足高密度和低灵敏度的要求，我们需要控制含能材料的晶体形态。我们使用改进的哈特曼 - 佩尔多克定理研究了1,1 - 二氨基 - 2,2 - 二硝基乙烯（FOX - 7）在二甲基亚砜/水混合溶剂中的晶体形态。利用分子动力学模拟确定了FOX - 7与溶剂之间的相互作用。结果表明，FOX - 7的晶体形状为六边形，在354 K时，（101）面是最大的暴露面，且与六个晶面相邻。随着温度降低，（001）面的面积显著减小。324 K时FOX - 7的晶体形态具有较小的纵横比4.72，该温度适合将形态从细长六边形调整为菱形。预测结果与实验结果显著吻合。此外，我们通过吉布斯 - 居里 - 伍尔夫定理预测了FOX - 7形态的演变路径，并解释了实际结晶过程中不同外部条件导致晶体形状变化的原因。
