Structure determination of ζ-N2 from single-crystal X-ray diffraction and theoretical suggestion for the formation of amorphous nitrogen

• Published in: Nature communications 2023-10, Vol.14 (1), p.6207-8, Article 6207
• Main Authors: Laniel, Dominique, Trybel, Florian, Aslandukov, Andrey, Spender, James, Ranieri, Umbertoluca, Fedotenko, Timofey, Glazyrin, Konstantin, Bright, Eleanor Lawrence, Chariton, Stella, Prakapenka, Vitali B., Abrikosov, Igor A., Dubrovinsky, Leonid, Dubrovinskaia, Natalia
• Format: Article
• Language: English
• Subjects: 140/133; 639/638/440/94; 639/766/119/1002; 639/766/94; Allotropy; Crystal structure; Density functional theory; Humanities and Social Sciences; Initiation (polymerization); Laser beam heating; Lattice vibration; multidisciplinary; Nitrogen; Polymerization; Science; Science & Technology - Other Topics; Science (multidisciplinary); Single crystals; Unit cell; Vibration mode; X-ray diffraction
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-41968-2

The allotropy of solid molecular nitrogen is the consequence of a complex interplay between fundamental intermolecular as well as intramolecular interactions. Understanding the underlying physical mechanisms hinges on knowledge of the crystal structures of these molecular phases. That is especially true for ζ-N 2 , key to shed light on nitrogen’s polymerization. Here, we perform single-crystal X-ray diffraction on laser-heated N 2 samples at 54, 63, 70 and 86 GPa and solve and refine the hitherto unknown structure of ζ-N 2 . In its monoclinic unit cell (space group C 2/ c ), 16 N 2 molecules are arranged in a configuration similar to that of ε-N 2 . The structure model provides an explanation for the previously identified Raman and infrared lattice and vibrational modes of ζ-N 2 . Density functional theory calculations give an insight into the gradual delocalization of electronic density from intramolecular bonds to intermolecular space and suggest a possible pathway towards nitrogen’s polymerization. The ζ-N 2 phase is key for comprehending the pressure-driven molecular to polymeric shift in nitrogen. Here, the authors resolved the crystal structure of ζ-N 2 and identified a gradual delocalization of its electronic density under pressure, culminating in the initiation of nitrogen’s polymerization.