Aromatic hexazine [N] anion featured in the complex structure of the high-pressure potassium nitrogen compound KN.

The recent high-pressure synthesis of pentazolates and the subsequent stabilization of the aromatic [N] anion at atmospheric pressure have had an immense impact on nitrogen chemistry. Other aromatic nitrogen species have also been actively sought, including the hexaazabenzene N ring. Although a variety of configurations and geometries have been proposed based on ab initio calculations, one that stands out as a likely candidate is the aromatic hexazine anion [N].

Subduction-related oxidation of the sublithospheric mantle evidenced by ferropericlase and magnesiowüstite diamond inclusions.

Ferropericlase (Mg,Fe)O is the second most abundant mineral in Earth's lower mantle and a common inclusion found in subcratonic diamonds. Pyrolitic mantle has Mg# (100 × Mg/(Mg+Fe)) ~89. However, ferropericlase inclusions in diamonds show a broad range of Mg# between 12 and 93.

Anionic N Macrocycles and a Polynitrogen Double Helix in Novel Yttrium Polynitrides YN and Y N at 100 GPa.

Two novel yttrium nitrides, YN and Y N , were synthesized by direct reaction between yttrium and nitrogen at 100 GPa and 3000 K in a laser-heated diamond anvil cell. High-pressure synchrotron single-crystal X-ray diffraction revealed that the crystal structures of YN and Y N feature a unique organization of nitrogen atoms-a previously unknown anionic N macrocycle and a polynitrogen double helix, respectively. Density functional theory calculations, confirming the dynamical stability of the YN and Y N compounds, show an anion-driven metallicity, explaining the unusual bond orders in the polynitrogen units.

A reentrant phase transition and a novel polymorph revealed in high-pressure investigations of CF up to 46.5 GPa.

The high-pressure behavior of simple molecular systems, devoid of strong intermolecular interactions, provides a unique avenue toward a fundamental understanding of matter. Tetrahalides of the carbon group elements (group 14), lacking all intermolecular interactions but van der Waals, are among the most elementary of molecular compounds. Here, we report the investigation of CF up to 46.

Revealing the Complex Nature of Bonding in the Binary High-Pressure Compound FeO_{2}.

Extreme pressures and temperatures are known to drastically affect the chemistry of iron oxides, resulting in numerous compounds forming homologous series nFeOmFe_{2}O_{3} and the appearance of FeO_{2}. Here, based on the results of in situ single-crystal x-ray diffraction, Mössbauer spectroscopy, x-ray absorption spectroscopy, and density-functional theory+dynamical mean-field theory calculations, we demonstrate that iron in high-pressure cubic FeO_{2} and isostructural FeO_{2}H_{0.5} is ferric (Fe^{3+}), and oxygen has a formal valence less than 2.