Synthesis of Ultra‐Incompressible and Recoverable Carbon Nitrides Featuring CN₄ Tetrahedra

Abstract

Carbon nitrides featuring 3D frameworks of CN4 tetrahedra were identified as one of the great aspirations of materials science, expected to have a hardness greater than or comparable to diamond. After more than three decades of efforts to synthesize them, no unambiguous evidence of their existence has been delivered. Here, we report the high‐pressure high‐temperature synthesis of three carbon‐nitrogen compounds, tI14‐C3N4, hP126‐C3N4, and tI24‐CN2, in laser‐heated diamond anvil cells. Their structures were solved and refined using synchrotron single‐crystal X‐ray diffraction. Physical properties investigations showed that these strongly covalently bonded materials, ultra‐incompressible and superhard, also possess high energy density, piezoelectric, and photoluminescence properties. The novel carbon nitrides are unique among high‐pressure materials, as being produced above 100 GPa they are recoverable in air at ambient conditions.This article is protected by copyright. All rights reserved

Stabilization Of The CN35− Anion In Recoverable High‐pressure Ln3O2(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) Oxoguanidinates

“…It was found to have the orthorhombic space group Pnma (#62) and lattice parameters a =9.2875(7) Å, b =6.8259(5) Å, c =6.149(2) Å at 54(1) GPa and a =9.795(2) Å, b =7.0062(11) Å, c =6.3699(11) Å at 25(1) GPa (see Tables S1–S2 and the CIFs for the full crystallographic data [18] ). The carbon atom in La 3 O 2 (CN 3 ) comes from the diamond anvil; the latter being able to act as a carbon source and participating in the chemical reactions is well known [19–21] …”

“…The carbon atom in La 3 O 2 (CN 3 ) comes from the diamond anvil; the latter being able to act as a carbon source and participating in the chemical reactions is well known. [19][20][21] After the La 3 O 2 (CN 3 ) synthesis at 54(1) GPa, the sample was decompressed in a few pressure steps down to ambient pressure, when the DAC was opened in air. SCXRD reflections from La 3 O 2 (CN 3 ) crystallites could be traced down to ambient conditions and persisted after air exposure (Table S3 and CIF for the full crystallographic data [18] ).…”

Computational Screening and Stabilization of Boron-Substituted Type-I and Type-II Carbon Clathrates

“…18 When combined with other light elements, carbon forms heterodiamond structures including SiC, BC 5 , and BC 2 N. 9,19,20 Recently, C 3 N 4 polytypes that were predicted to be less compressible than diamond were produced under highpressure conditions. 21,22 Clathrates represent another class of 3D network structures. Clathrates are constructed from tetrahedral building blocks that form polyhedral cages capable of holding guest atoms or molecules.…”

Simple Molecules under High‐Pressure and High‐Temperature Conditions: Synthesis and Characterization of α‐ and β‐C(NH)2 with Fully sp3‐Hybridized Carbon

“…[4] Building on this approach, Laniel et al were able to synthesize the first true carbon(IV) nitrides C 3 N 4 and carbon pernitride CN 2 by nitridation of tetracyanoethylene at pressures higher than 70 GPa. [5] tI14-C 3 N 4 crystallizes in a defect sphalerite structure, while hP126-C 3 N 4 has a structure similar but not identical to β-Si 3 N 4 . In contrast to HPHT CO 2 phases, all four C/N phases can be recovered to ambient conditions and the bulk moduli K 0 of hP126-C 3 N 4 (417 GPa) and CN 2 (419 GPa) almost reach that of diamond (446 GPa).…”

“…In contrast to HPHT CO 2 phases, all four C/N phases can be recovered to ambient conditions and the bulk moduli K 0 of hP126-C 3 N 4 (417 GPa) and CN 2 (419 GPa) almost reach that of diamond (446 GPa). [5] Opposite to the binary systems, little is known about the chemistry of the ternary systems. Of these, C/N/H is extremely attractive from a materials science perspective since HPHT phases of these three elements should contain imide-groups.…”