A novel all-nitrogen molecular crystal N 16 as a promising high-energy-density material
A novel all-nitrogen molecular crystal N 16 as a promising high-energy-density material
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一种新型全氮分子晶体N 16 作为一种有前途的高能量密度材料
DOI：
10.1039/d2dt00820c
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发表时间：
2022
影响因子：
4
通讯作者：
Miao, Mao-sheng
中科院分区：
文献类型：
--
作者：
Zhao, Lei;Liu, Shijie;Chen, Yuanzheng;Yi, Wencai;Khodagholian, Darlar;Gu, Fenglong;Kelson, Eric;Zheng, Yonghao;Liu, Bingbing;Miao, Mao-sheng
全氮固体，如果成功合成，是理想的高能量密度材料，因为它们储存了大量的能量，分解时只产生无害的氮气。目前，获得全氮固体的唯一方法是对氮气晶体施加高压。然而，像CG-N这样的产品在释放压力时往往会分解。与共价固体相比，分子晶体在减压过程中更有可能保持稳定，因为它们可以通过增加分子间距离来松弛应变。这种路线的挑战是找到一种分子晶体，它可以在加压下获得有利的相。在这项工作中，我们通过设计一种新型的N16分子(三五唑胺)并研究其在一系列压力下的晶体结构，证明了芳香族单元和高分子对称性是实现全氮分子晶体的关键因素。密度泛函计算和结构研究表明，这种新的全氮分子晶体由于其高度对称的分子的高效晶体堆积，随着压力的增加表现出特别缓慢的热焓增加。振动模计算和分子动力学(MD)模拟表明，N16晶体在常压下是亚稳态的，并可在400K以下保持不活跃。分解的初始反应步骤是按照分子动力学模拟揭示的N5基团中的N_2协同切除的路径来计算的。
All-nitrogen solids, if successfully synthesized, are ideal high-energy-density materials because they store a great amount of energy and produce only harmless N2 gas upon decomposition. Currently, the only method to obtain all-nitrogen solids is to apply high pressure to N2 crystals. However, products such as cg-N tend to decompose upon releasing the pressure. Compared to covalent solids, molecular crystals are more likely to remain stable during decompression because they can relax the strain by increasing the intermolecular distances. The challenge of such a route is to find a molecular crystal that can attain a favorable phase under elevated pressure. In this work, we show, by designing a novel N16 molecule (tripentazolylamine) and examining its crystal structures under a series of pressures, that the aromatic units and high molecular symmetry are the key factors to achieving an all-nitrogen molecular crystal. Density functional calculations and structural studies reveal that this new all-nitrogen molecular crystal exhibits a particularly slow enthalpy increase with pressure due to the highly efficient crystal packing of its highly symmetric molecules. Vibration mode calculations and molecular dynamics (MD) simulations show that N16 crystals are metastable at ambient pressure and could remain inactive up to 400 K. The initial reaction steps of the decomposition are calculated by following the pathway of the concerted excision of N2 from the N5 group as revealed by the MD simulations.