Wei Shuli, Lian Lili, Liu Yan, Li Da, Liu Zhao, Cui Tian
School of Physics and Optoelectronic Engineering, Shandong University of Technology, 250049 Zibo, China.
Phys Chem Chem Phys. 2020 Mar 7;22(9):5242-5248. doi: 10.1039/c9cp05745e. Epub 2020 Feb 24.
High-pressure technology can help us to obtain excellent materials. We have explored alkaline-earth-metal strontium nitrides under different pressures, theoretically. A variety of stable Sr-N structures were predicted by the structure searching method using CALYPSO code. Six new stoichiometries, SrN, SrN, SrN, SrN, SrN, and SrN, were predicted. And our calculation proved that all these compounds were stable existing under ambient pressure up to 100 GPa. A rich variety of poly-nitrogen forms appeared in the newly predicted SrN compounds, including four nitrogen polymerization forms: ranging from N, N, N, and N molecules, to zig-zag nitrogen chains and extended chains connected by puckered "N" rings. Significantly, the 1D extended polymeric chain of puckered "N" rings was firstly identified in the P1[combining macron]-SrN structure at 60 GPa. Another N-rich C2/c-SrN was stable only under the relatively high-pressure of 20 GPa, but this phase can be quenched under atmospheric pressure. The N-rich phase SrN maintained structural stability when the pressure reached 50-70 GPa. The delocalization of π electrons from N atoms was the principal cause for its metallicity in SrN. In this paper, our calculated results indicated that the energetic poly-nitrides in alkaline-earth-metal nitrides can be obtained by the high-pressure method.
高压技术有助于我们获得优质材料。我们从理论上探索了不同压力下的碱土金属锶氮化物。使用CALYPSO代码通过结构搜索方法预测了多种稳定的Sr-N结构。预测了六种新的化学计量比，即SrN、SrN、SrN、SrN、SrN和SrN。我们的计算证明，所有这些化合物在高达100 GPa的环境压力下都能稳定存在。新预测的SrN化合物中出现了丰富多样的多氮形式，包括四种氮聚合形式：从N₂、N₃、N₄和N₅分子，到锯齿状氮链以及由褶皱“N”环连接的延伸链。值得注意的是，在60 GPa下的P1̅-SrN结构中首次发现了由褶皱“N”环构成的一维延伸聚合物链。另一种富氮的C2/c-SrN仅在20 GPa的相对高压下稳定，但该相在大气压下可以淬火。当压力达到50 - 70 GPa时，富氮相SrN保持结构稳定性。N原子的π电子离域是其在SrN中具有金属性的主要原因。在本文中，我们的计算结果表明，通过高压方法可以获得碱土金属氮化物中的高能多氮化物。
