High-Pressure Synthesis of oP28-C₃N₄ Recoverable to Ambient Conditions

Titelangaben

Laniel, Dominique ; Trybel, Florian ; Zhou, Wenju ; Aslandukov, Andrii ; Spender, James ; Tasnádi, Ferenc ; Fedotenko, Timofey ; Ranieri, Umbertoluca ; Liang, Akun ; Aslandukova, Alena ; Akbar, Fariia Iasmin ; Yin, Yuqing ; Chariton, Stella ; Pakhomova, Anna ; Garbarino, Gaston ; Mezouar, Mohamed ; Hanfland, Michael ; Prakapenka, Vitali ; Abrikosov, Igor A. ; Dubrovinsky, Leonid ; Dubrovinskaia, Natalia:
High-Pressure Synthesis of oP28-C₃N₄ Recoverable to Ambient Conditions.
In: Advanced Functional Materials. Bd. 35 (2025) Heft 11 . - 2416892.
ISSN 1616-3028
DOI: https://doi.org/10.1002/adfm.202416892

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Abstract

The thermodynamic parameter pressure is ideal for producing novel ultraincompressible and superhard materials as it promotes the formation of polymeric frameworks and higher atomic coordination. In this regard, carbon and nitrogen are particularly attractive elements as they can produce extended arrangements of strong covalent bonds. In this study, a previously unobserved C3N4 polymorph, denoted as oP28-C3N4 (Pnnm, #58), is synthesized at pressures between 73 and 104 GPa in laser-heated diamond anvil cells and found recoverable to ambient conditions and stable in air. The crystal structure of oP28-C3N4, comprised of corner-sharing CN4 tetrahedra, is solved and refined using synchrotron single-crystal X-ray diffraction. With a bulk modulus of 334(3) GPa deduced from experimental data, the compound is highly incompressible. Based on macroscopic and microscopic calculations, its hardness may achieve 47.5 or 79.7 GPa, respectively, making it a superhard material. Incompressibility of CN4 tetrahedra in all experimentally observed C3N4 polymorphs is found to be greater than that of the CC4 and BN4 tetrahedra forming the structures of diamond and cubic boron nitride. Density functional theory calculations provide further insight into the electronic, vibrational, and mechanical properties of oP28-C3N4, as well as their stability relative to other C─N phases.