Yi Wencai, Jiang Xingang, Yang Tao, Yang Bingchao, Liu Zhen, Liu Xiaobing
Laboratory of High Pressure Physics and Material Science (HPPMS), School of Physics and Physical Engineering, Qufu Normal University, Qufu 273165, China.
College of Chemistry, Jilin University, Changchun 130021, Jilin, China.
ACS Omega. 2020 Sep 16;5(38):24946-24953. doi: 10.1021/acsomega.0c03835. eCollection 2020 Sep 29.
Recently, it has been reported that high-pressure synthesized lithium pentazolates could be quenched down to ambient conditions. However, the crystalline structures of LiN under ambient conditions are still ambiguous. In this work, the structures of LiN compound were directly explored at atmospheric pressure by using a new constrain structure search method. By using this method, three new allotropes were confirmed, and they show lower energy than the previous reported LiN phases. Both their thermodynamic and dynamic stability were confirmed through formation enthalpies, phonon spectrum, and ab initio molecular dynamics simulations under ambient conditions. Moreover, these three allotropes show similar formation enthalpies and properties, which suggests that it is hard to obtain a single LiN phase, which is well consistent with the experimental phenomenon. Furthermore, because of their low formation energy, all of them possess low energy density when they directly decompose to LiN and nitrogen (0.52 kJ/g). Instead, the decomposed energy could be further improved to 3.78 kJ/g when they decompose under an oxygen-rich environment.
最近，有报道称高压合成的五唑酸锂可以被淬冷至环境条件。然而，环境条件下LiN的晶体结构仍然不明确。在这项工作中，通过使用一种新的约束结构搜索方法，在常压下直接探索了LiN化合物的结构。通过使用这种方法，确认了三种新的同素异形体，并且它们显示出比先前报道的LiN相更低的能量。通过环境条件下的生成焓、声子谱和从头算分子动力学模拟，证实了它们的热力学和动力学稳定性。此外，这三种同素异形体显示出相似的生成焓和性质，这表明很难获得单一的LiN相，这与实验现象非常一致。此外，由于它们的生成能量较低，当它们直接分解为LiN和氮气时，它们都具有较低的能量密度（0.52 kJ/g）。相反，当它们在富氧环境下分解时，分解能量可以进一步提高到3.78 kJ/g。
