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Here, we present the synthesis of a novel quaternary compound, iodide carbonate Na5(CO3)2I, at 18(1) and 25.1(5) GPa in laser-heated diamond anvil cells. Single-crystal synchrotron X-ray diffraction provides accurate structural data for Na5(CO3)2I and shows that the structure of the material can be described as built of INa8 square prisms, distorted NaO6 octahedra, and trigonal planar CO32− units. Decompression experiments show that the novel iodide carbonate is recoverable in the N2 atmosphere to ambient conditions. Our ab initio calculations agree well with the experimental structural data, provide the equation of state, and shed light on the chemical bonding and electronic properties of the new compound. [ABSTRACT FROM AUTHOR]

A series of isostructural Ln3O2(CN3) (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 Ln3O2(CN3) solids are composed of the hitherto unknown CN35− guanidinate anion—deprotonated guanidine. Changes in unit cell volumes and compressibility of Ln3O2(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) compounds are found to be dictated by the lanthanide contraction phenomenon. Decompression experiments show that Ln3O2(CN3) compounds are recoverable to ambient conditions. The stabilization of the CN35− guanidinate anion at ambient conditions provides new opportunities in inorganic and organic synthetic chemistry. [ABSTRACT FROM AUTHOR]

Non‐metal nitrides are an exciting field of chemistry, featuring a significant number of compounds that can possess outstanding material properties. These properties mainly rely on maximizing the number of strong covalent bonds, with crosslinked XN6 octahedra frameworks being particularly attractive. In this study, the phosphorus–nitrogen system was studied up to 137 GPa in laser‐heated diamond anvil cells, and three previously unobserved phases were synthesized and characterized by single‐crystal X‐ray diffraction, Raman spectroscopy measurements and density functional theory calculations. δ‐P3N5 and PN2 were found to form at 72 and 134 GPa, respectively, and both feature dense 3D networks of the so far elusive PN6 units. The two compounds are ultra‐incompressible, having a bulk modulus of K0=322 GPa for δ‐P3N5 and 339 GPa for PN2. Upon decompression below 7 GPa, δ‐P3N5 undergoes a transformation into a novel α′‐P3N5 solid, stable at ambient conditions, that has a unique structure type based on PN4 tetrahedra. The formation of α′‐P3N5 underlines that a phase space otherwise inaccessible can be explored through materials formed under high pressure. [ABSTRACT FROM AUTHOR]

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, Y2Cl and DyCl, and chloride carbides, Y2ClC and Dy2ClC, were synthesized at ~40 GPa and 2000 K and their structures were solved and refined using in situ single-crystal synchrotron X-ray diffraction. Also, FeCl2 with the HP-PdF2-type structure, previously reported at 108 GPa, was synthesized at ~160 GPa and 2100 K. The results of our ab initio calculations fully support experimental findings and reveal the electronic structure and chemical bonding in these compounds. The chemical stability of alkali halides has caused them to be exploited as inert media in high-pressure, high-temperature experiments. Here, NaCl and KCl are unexpectedly found to react with yttrium, dysprosium and iron oxide in a laser-heated diamond anvil cell, producing Y2Cl, DyCl, Y2ClC and Dy2ClC at ~40 GPa and 2000 K and FeCl2 at ~160 GPa and 2100 K. [ABSTRACT FROM AUTHOR]

Exploring the chemistry of materials at high pressure leads to discoveries of previously unknown compounds and phenomena. Here chemical reactions between elemental dysprosium and carbon were studied in laser-heated diamond anvil cells at pressures up to 95 GPa and temperatures of ∼2800 K. In situ single-crystal synchrotron X-ray diffraction (SCXRD) analysis of the reaction products revealed the formation of novel dysprosium carbides, γ-DyC 2 , Dy 5 C 9 , and γ-Dy 4 C 5 , along with previously reported Dy 3 C 2 and Dy 4 C 3. The crystal structures of γ-DyC 2 and Dy 5 C 9 feature infinite flat carbon polyacene-like ribbons and cis -polyacetylene-type chains, respectively. In the structure of γ-Dy 4 C 5 , carbon atoms form dimers and non-linear trimers. Dy 3 C 2 contains ethanide-type carbon dumbbells, and Dy 4 C 3 is methanide featuring single carbon atoms. Density functional theory calculations reproduce well the crystal structures of high-pressure dysprosium carbides and reveal conjugated π -electron systems in novel infinite carbon polyanions. This work demonstrates that complex carbon homoatomic species previously unknown in organic chemistry can be synthesized at high pressures by direct reactions of carbon with metals. [Display omitted] [ABSTRACT FROM AUTHOR]

Non‐metal nitrides are an exciting field of chemistry, featuring a significant number of compounds that can possess outstanding material properties. These properties mainly rely on maximizing the number of strong covalent bonds, with crosslinked XN6 octahedra frameworks being particularly attractive. In this study, the phosphorus–nitrogen system was studied up to 137 GPa in laser‐heated diamond anvil cells, and three previously unobserved phases were synthesized and characterized by single‐crystal X‐ray diffraction, Raman spectroscopy measurements and density functional theory calculations. δ‐P3N5 and PN2 were found to form at 72 and 134 GPa, respectively, and both feature dense 3D networks of the so far elusive PN6 units. The two compounds are ultra‐incompressible, having a bulk modulus of K0=322 GPa for δ‐P3N5 and 339 GPa for PN2. Upon decompression below 7 GPa, δ‐P3N5 undergoes a transformation into a novel α′‐P3N5 solid, stable at ambient conditions, that has a unique structure type based on PN4 tetrahedra. The formation of α′‐P3N5 underlines that a phase space otherwise inaccessible can be explored through materials formed under high pressure. [ABSTRACT FROM AUTHOR]