High-Pressure 16-YBr Polymorph Recoverable to Ambient Conditions: From 3D Framework to Layered Material.

Exfoliation of graphite and the discovery of the unique properties of graphene─graphite's single layer─have raised significant attention to layered compounds as potential precursors to 2D materials with applications in optoelectronics, spintronics, sensors, and solar cells. In this work, a new orthorhombic polymorph of yttrium bromide, 16-YBr was synthesized from yttrium and CBr in a laser-heated diamond anvil cell at 45 GPa and 3000 K. The structure of 16-YBr was solved and refined using in situ synchrotron single-crystal X-ray diffraction.

Synthesis of LaCN, TbCN, CeCN, and TbCN Polycarbonitrides at Megabar Pressures.

Inorganic ternary metal-C-N compounds with covalently bonded C-N anions encompass important classes of solids such as cyanides and carbodiimides, well known at ambient conditions and composed of [CN] and [CN] anions, as well as the high-pressure formed guanidinates featuring [CN] anion. At still higher pressures, carbon is expected to be 4-fold coordinated by nitrogen atoms, but hitherto, such CN-built anions are missing. In this study, four polycarbonitride compounds (LaCN, TbCN, CeCN, and TbCN) are synthesized in laser-heated diamond anvil cells at pressures between 90 and 111 GPa.

Extending carbon chemistry at high-pressure by synthesis of CaC and CaC with deprotonated polyacene- and para-poly(indenoindene)-like nanoribbons.

Metal carbides are known to contain small carbon units similar to those found in the molecules of methane, acetylene, and allene. However, for numerous binary systems ab initio calculations predict the formation of unusual metal carbides with exotic polycarbon units, [C] rings, and graphitic carbon sheets at high pressure (HP). Here we report the synthesis and structural characterization of a HP-CaC polymorph and a CaC compound featuring deprotonated polyacene-like and para-poly(indenoindene)-like nanoribbons, respectively.

Diverse high-pressure chemistry in Y-NHBH and Y-paraffin oil systems.

The yttrium-hydrogen system has gained attention because of near-ambient temperature superconductivity reports in yttrium hydrides at high pressures. We conducted a study using synchrotron single-crystal x-ray diffraction (SCXRD) at 87 to 171 GPa, resulting in the discovery of known (two YH phases) and five previously unknown yttrium hydrides. These were synthesized in diamond anvil cells by laser heating yttrium with hydrogen-rich precursors-ammonia borane or paraffin oil.

Stabilization of N and N anionic units and 2D polynitrogen layers in high-pressure scandium polynitrides.

Nitrogen catenation under high pressure leads to the formation of polynitrogen compounds with potentially unique properties. The exploration of the entire spectrum of poly- and oligo-nitrogen moieties is still in its earliest stages. Here, we report on four novel scandium nitrides, ScN, ScN, ScN and ScN, synthesized by direct reaction between yttrium and nitrogen at 78-125 GPa and 2500 K in laser-heated diamond anvil cells.

Synthesis of Ultra-Incompressible and Recoverable Carbon Nitrides Featuring CN Tetrahedra.

Carbon nitrides featuring three-dimensional frameworks of CN tetrahedra are 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, the high-pressure high-temperature synthesis of three carbon-nitrogen compounds, tI14-C N , hP126-C N , and tI24-CN , in laser-heated diamond anvil cells, is reported.

Stabilization Of The CN Anion In Recoverable High-pressure Ln O (CN ) (Ln=La, Eu, Gd, Tb, Ho, Yb) Oxoguanidinates.

A series of isostructural Ln O (CN ) (Ln=La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates was synthesized under high-pressure (25-54 GPa) high-temperature (2000-3000 K) conditions in laser-heated diamond anvil cells. The crystal structure of this novel class of compounds was determined via synchrotron single-crystal X-ray diffraction (SCXRD) as well as corroborated by X-ray absorption near edge structure (XANES) measurements and density functional theory (DFT) calculations. The Ln O (CN ) solids are composed of the hitherto unknown CN guanidinate anion-deprotonated guanidine.

Unraveling the Bonding Complexity of Polyhalogen Anions: High-Pressure Synthesis of Unpredicted Sodium Chlorides NaCl and NaCl and Bromide NaBr.

The field of polyhalogen chemistry, specifically polyhalogen anions (polyhalides), is rapidly evolving. Here, we present the synthesis of three sodium halides with unpredicted chemical compositions and structures (10-NaCl, 18-NaCl, and 18-NaBr), a series of isostructural cubic 8-AX halides (NaCl, KCl, NaBr, and KBr), and a trigonal potassium chloride (24-KCl). The high-pressure syntheses were realized at 41-80 GPa in diamond anvil cells laser-heated at about 2000 K.

High-pressure synthesis of dysprosium carbides.

Chemical reactions between dysprosium and carbon were studied in laser-heated diamond anvil cells at pressures of 19, 55, and 58 GPa and temperatures of ∼2500 K. single-crystal synchrotron X-ray diffraction analysis of the reaction products revealed the formation of novel dysprosium carbides, DyC and DyC, and dysprosium sesquicarbide DyC previously known only at ambient conditions. The structure of DyC was found to be closely related to that of dysprosium sesquicarbide DyC with the PuC-type structure.

Synthesis of rare-earth metal compounds through enhanced reactivity of alkali halides at high pressures.

Chemical stability of the alkali halides NaCl and KCl has allowed for their use as inert media in high-pressure high-temperature experiments. Here we demonstrate the unexpected reactivity of the halides with metals (Y, Dy, and Re) and iron oxide (FeO) in a laser-heated diamond anvil cell, thus providing a synthetic route for halogen-containing binary and ternary compounds. So far unknown chlorides, YCl and DyCl, and chloride carbides, YClC and DyClC, were synthesized at ~40 GPa and 2000 K and their structures were solved and refined using in situ single-crystal synchrotron X-ray diffraction.