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Prediction of Stable Iron Nitrides at Ambient and High Pressures with Progressive Formation of New Polynitrogen Species
Chemistry of Materials ( IF 7.2 ) Pub Date : 2018-11-07 00:00:00 , DOI: 10.1021/acs.chemmater.8b02972
Lailei Wu 1 , Ruifeng Tian 1 , Biao Wan 1, 2 , Hanyu Liu 3, 4 , Ning Gong 1 , Peng Chen 1 , Tongde Shen 1 , Yansun Yao 5 , Huiyang Gou 2, 6 , Faming Gao 6
Chemistry of Materials ( IF 7.2 ) Pub Date : 2018-11-07 00:00:00 , DOI: 10.1021/acs.chemmater.8b02972
Lailei Wu 1 , Ruifeng Tian 1 , Biao Wan 1, 2 , Hanyu Liu 3, 4 , Ning Gong 1 , Peng Chen 1 , Tongde Shen 1 , Yansun Yao 5 , Huiyang Gou 2, 6 , Faming Gao 6
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Nitride materials are of considerable interest due to their fundamental importance and practical applications. However, synthesis of transition metal nitrides often requires extreme conditions, e.g., high temperature and/or high pressure, slowing down the experimental discovery. Using global structure search methods in combination with first-principles calculations, we systematically explore the stoichiometric phase space of iron–nitrogen compounds on the nitrogen-rich side at ambient and high pressures up to 100 GPa. Diverse stoichiometries in the Fe–N system are found to emerge in the phase diagram at high pressures. Significantly, FeN4 is found to be stable already at ambient pressure. It undergoes a polymerization near 20 GPa which results in a high energy density. Accompanying the polymerization, FeN4 transforms from a direct band gap semiconductor to ferromagnetic metal. We also predict several phase transitions in FeN and FeN2 at high pressure, and the results explain the previous experimental observations by comparing the X-ray diffraction patterns. Stepwise formation of polynitrogen species is observed following the increment of nitrogen content in the stoichiometry, from isolated N atoms in FeN, to the N2 unit in FeN2 and Fe3N8, to the N6 unit in Fe3N8 and FeN3, and to the N∞ chain in FeN4, FeN6, and FeN8. Ultra-incompressibility is found in marcasite-FeN2, FeN3, and FeN4 along particular crystalline directions, while high energy density, 1.37–2.02 kJ g–1, is expected for FeN4, FeN6, and FeN8. Our results shed light on understanding the chemistry of transition metal polynitrides under pressure and encourage experimental synthesis of newly predicted iron nitrides in the near future.
中文翻译：
逐步形成新的多氮物质，可预测常压和高压下稳定的铁氮化物
氮化物材料由于其基本重要性和实际应用而备受关注。然而，过渡金属氮化物的合成通常需要极端条件，例如高温和/或高压，这减慢了实验发现。使用整体结构搜索方法与第一性原理计算相结合，我们系统地探索了在环境压力和高达100 GPa的高压下，富氮侧铁-氮化合物的化学计量相空间。在高压下，相图中发现了Fe–N系统中不同的化学计量。明显地，发现FeN 4在环境压力下已经稳定。它在接近20 GPa的压力下进行聚合，从而导致高能量密度。伴随聚合，FeN图4从直接带隙半导体转变为铁磁金属。我们还预测了FeN和FeN 2在高压下的几个相变，结果通过比较X射线衍射图解释了先前的实验观察结果。随着化学计量中氮含量的增加，从FeN中的孤立N原子到FeN 2和Fe 3 N 8中的N 2单元，再到Fe 3 N 8和FeN中的N 6单元，随着观察到氮含量的增加，逐步观察到多氮物质的形成。3，和N个∞在FEN链4，FEN 6，和FEN8。在镁铁矿的FeN 2，FeN 3和FeN 4中沿特定的结晶方向发现了超不可压缩性，而FeN 4，FeN 6和FeN 8的高能量密度为1.37–2.02 kJ g –1。我们的研究结果有助于理解在压力下过渡金属聚氮化物的化学性质，并鼓励在不久的将来通过实验合成新预测的氮化铁。
更新日期：2018-11-07
中文翻译：
逐步形成新的多氮物质，可预测常压和高压下稳定的铁氮化物
氮化物材料由于其基本重要性和实际应用而备受关注。然而，过渡金属氮化物的合成通常需要极端条件，例如高温和/或高压，这减慢了实验发现。使用整体结构搜索方法与第一性原理计算相结合，我们系统地探索了在环境压力和高达100 GPa的高压下，富氮侧铁-氮化合物的化学计量相空间。在高压下，相图中发现了Fe–N系统中不同的化学计量。明显地，发现FeN 4在环境压力下已经稳定。它在接近20 GPa的压力下进行聚合，从而导致高能量密度。伴随聚合，FeN图4从直接带隙半导体转变为铁磁金属。我们还预测了FeN和FeN 2在高压下的几个相变，结果通过比较X射线衍射图解释了先前的实验观察结果。随着化学计量中氮含量的增加，从FeN中的孤立N原子到FeN 2和Fe 3 N 8中的N 2单元，再到Fe 3 N 8和FeN中的N 6单元，随着观察到氮含量的增加，逐步观察到多氮物质的形成。3，和N个∞在FEN链4，FEN 6，和FEN8。在镁铁矿的FeN 2，FeN 3和FeN 4中沿特定的结晶方向发现了超不可压缩性，而FeN 4，FeN 6和FeN 8的高能量密度为1.37–2.02 kJ g –1。我们的研究结果有助于理解在压力下过渡金属聚氮化物的化学性质，并鼓励在不久的将来通过实验合成新预测的氮化铁。
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