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标题：Exotic stable cesium polynitrides at high pressure
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作者：Feng Peng ; Yunxia Han ; Hanyu Liu 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2015
卷号：5
DOI：10.1038/srep16902
出版社：Springer Nature
摘要：New polynitrides containing metastable forms of nitrogen are actively investigated as potential high-energy-density materials. Using a structure search method based on the CALYPSO methodology, we investigated the stable stoichiometries and structures of cesium polynitrides at high pressures. Along with the CsN₃, we identified five new stoichiometric compounds (Cs₃N, Cs₂N, CsN, CsN₂, and CsN₅) with interesting structures that may be experimentally synthesizable at modest pressures ( i.e. , less than 50 GPa). Nitrogen species in the predicted structures have various structural forms ranging from single atom (N) to highly endothermic molecules (N₂, N₃, N₄, N₅, N₆) and chains (N_∞). Polymeric chains of nitrogen were found in the high-pressure C 2/ c phase of CsN₂. This structure contains a substantially high content of single N-N bonds that exceeds the previously known nitrogen chains in pure forms, and also exhibit metastability at ambient conditions. We also identified a very interesting CsN crystal that contains novel N₄⁴⁻ anion. To our best knowledge, this is the first time a charged N₄ species being reported. Results of the present study suggest that it is possible to obtain energetic polynitrogens in main-group nitrides under high pressure.