title: Exotic stable cesium polynitrides at high pressure.
abstract: 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 C2/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 N4(4-) 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.
authors.affiliation: College of Physics and Electronic Information, Luoyang Normal University, Luoyang 471022, China.|Beijing Computational Science Research Center, Beijing 10084, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Peng
authors.affiliation: College of Physics and Electronic Information, Luoyang Normal University, Luoyang 471022, China.
authors.forename: Yunxia
authors.initials: Y
authors.lastname: Han
authors.affiliation: Geophysical Laboratory, Carnegie Institution of Washington, NW, Washington, D.C. 20015, USA.
authors.forename: Hanyu
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E2, Canada.|Canadian Light Source, Saskatoon, Saskatchewan, S7N 2V3 Canada.
authors.forename: Yansun
authors.initials: Y
authors.lastname: Yao