Polymeric nitrogen: A review of experimental synthesis method, structure properties and lattice dynamic characterization from large scientific facilities and extreme spectroscopy perspectives

Single-bonded polymeric nitrogen (PN) synthesized under high pressure was highly delivered for its valuable application prospects on high-energy-density materials (HEDM) and profound effects for understanding the interaction behavior of simple diatomic. Since the 1980s, polymeric phases of nitrogen have displayed remarkable complexity under extreme conditions of pressure and temperature that fascinated theoreticians and experimentalists. The high-pressure X-ray diffraction (XRD) and Raman spectroscopy experiments on PN made it possible to elucidate their evolution, in particular, to measure important structural information through scientific facilities. Here, the synthesized PN hitherto, including cubic gauche nitrogen (cg-N), layered polymeric nitrogen (LP-N), hexagonal layered polymeric nitrogen (HLP-N), post-layered-polymeric nitrogen (PLP-N), and black phosphorous structure nitrogen (BP–N) are reviewed. The synthesized methods, diagnosed technologies, lattice dynamics, and experimental challenges are introduced, with a particular focus on their structural similarity and lattice dynamic characterization, and the Raman criterion for nitrogen polymerization is also given. Finally, we propose the expectation of developing free-electron laser (FEL) and high-pressure neutron technology which is a potential key in the research of fundamental elements under high pressure.