Wang Yu, Bykov Maxim, Chepkasov Ilya, Samtsevich Artem, Bykova Elena, Zhang Xiao, Jiang Shu-Qing, Greenberg Eran, Chariton Stella, Prakapenka Vitali B, Oganov Artem R, Goncharov Alexander F
Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei, China.
Earth and Planets Laboratory, Carnegie Institution of Washington, Washington, DC, USA.
Nat Chem. 2022 Jul;14(7):794-800. doi: 10.1038/s41557-022-00925-0. Epub 2022 Apr 21.
Polynitrogen molecules are attractive for high-energy-density materials due to energy stored in nitrogen-nitrogen bonds; however, it remains challenging to find energy-efficient synthetic routes and stabilization mechanisms for these compounds. Direct synthesis from molecular dinitrogen requires overcoming large activation barriers and the reaction products are prone to inherent inhomogeneity. Here we report the synthesis of planar N hexazine dianions, stabilized in KN, from potassium azide (KN) on laser heating in a diamond anvil cell at pressures above 45 GPa. The resulting KN, which exhibits a metallic lustre, remains metastable down to 20 GPa. Synchrotron X-ray diffraction and Raman spectroscopy were used to identify this material, through good agreement with the theoretically predicted structural, vibrational and electronic properties for KN. The N rings characterized here are likely to be present in other high-energy-density materials stabilized by pressure. Under 30 GPa, an unusual N-containing compound with the formula K(N) was formed instead.
多氮分子因其氮氮键中储存的能量而对高能量密度材料具有吸引力；然而，为这些化合物找到节能的合成路线和稳定机制仍然具有挑战性。从分子态二氮直接合成需要克服巨大的活化能垒，并且反应产物易于出现固有不均匀性。在此我们报告了在金刚石对顶砧池中于45吉帕以上压力下激光加热叠氮化钾（KN₃）时合成了稳定于KN中的平面N₆六嗪二价阴离子。所得的具有金属光泽的KN在压力降至20吉帕时仍保持亚稳态。通过与理论预测的KN的结构、振动和电子性质良好吻合，利用同步加速器X射线衍射和拉曼光谱对该材料进行了鉴定。此处表征的N₆环可能存在于其他通过压力稳定的高能量密度材料中。在30吉帕以下，反而形成了一种化学式为K(N₃)的不寻常含氮化合物。
