Crystal Structure of New Carbon–Nitride-Related Material C 2 N 2 (CH 2 )

• Published in: Japanese Journal of Applied Physics 2011-09, Vol.50 (9R), p.95503
• Main Authors: Sougawa, Masaya, Sumiya, Takahiro, Takarabe, Kenichi, Mori, Yoshihisa, Okada, Taku, Gotou, Hirotada, Yagi, Takehiko, Yamazaki, Daisuke, Tomioka, Naotaka, Katsura, Tomoo, Kariyazaki, Hiroaki, Sueoka, Koji, Kunitsugu, Shinsuke
• Format: Article
• Language: English
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.50.095503

A new carbon–nitride-related C 2 N 2 (CH 2 ) nanoplatelet was synthesized by subjecting a precursor C 3 N 4 H x O y nanoparticle in a laser-heating diamond anvil cell to the pressure of 40 GPa and temperature of 1200–2000 K. The C and N composition of the quenched sample was determined to be C 3 N 2 by using an energy dispersive X-ray spectroscope attached to a transmission electron microscope. The crystal structure and atomic positions of this C 3 N 2 were obtained through Rietveld analysis of the X-ray diffraction pattern measured using synchrotron radiation. The hydrogen composition was difficult to determine experimentally because of the several-hundred-nanometer dimensions of the sample. First-principles calculation was alternatively used to discover the hydrogen composition. The synthesized C 2 N 2 (CH 2 ) was accordingly found to be an orthorhombic unit cell of the space group C m c 2 1 with lattice constants a = 7.625 Å, b = 4.490 Å, and c = 4.047 Å. If the CH 2 atomic unit is replaced with the CN 2 atomic unit and the bonding rearranged, the C 2 N 2 (CH 2 ) becomes the expected superhard C 3 N 4 .