Realization of an Ideal Cairo Tessellation in Nickel Diazenide NiN2: High-Pressure Route to Pentagonal 2D Materials

• Published in: ACS nano Vol. 15; no. 8; pp. 13539 - 13546
• Main Authors: Bykov, Maxim, Bykova, Elena, Ponomareva, Alena V, Tasnádi, Ferenc, Chariton, Stella, Prakapenka, Vitali B, Glazyrin, Konstantin, Smith, Jesse S, Mahmood, Mohammad F, Abrikosov, Igor A, Goncharov, Alexander F
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 24.08.2021; American Chemical Society (ACS)
• Subjects: chemical structure; diazenides; diffraction; high pressure; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; layers; metals; nitrides; penta-graphene; pentagonal 2D materials; two dimensional materials; pentagonal 2D materials; nitrides; diazenides; high pressure; penta-graphene
• ISSN: 1936-0851; 1936-086X; 1936-086X
• DOI: 10.1021/acsnano.1c04325

Most of the studied two-dimensional (2D) materials are based on highly symmetric hexagonal structural motifs. In contrast, lower-symmetry structures may have exciting anisotropic properties leading to various applications in nanoelectronics. In this work we report the synthesis of nickel diazenide NiN2 which possesses atomic-thick layers comprised of Ni2N3 pentagons forming Cairo-type tessellation. The layers of NiN2 are weakly bonded with the calculated exfoliation energy of 0.72 J/m2, which is just slightly larger than that of graphene. The compound crystallizes in the space group of the ideal Cairo tiling (P4/mbm) and possesses significant anisotropy of elastic properties. The single-layer NiN2 is a direct-band-gap semiconductor, while the bulk material is metallic. This indicates the promise of NiN2 to be a precursor of a pentagonal 2D material with a tunable direct band gap.