We show, by single crystal diffraction studies in laser-heated diamond anvil cells, that Ca 2 CO orthocarbonate, which contains CO 4 4tetrahedra, can be formed already at ~20 GPa at ~1830 K, i.e. at much lower pressures than other carbonates with sp 3-hybridized carbon. Ca 2 CO can also be formed at ~89 GPa and ~2500 K. This very broad p, T-range suggests the possible existence of Ca 2 CO 4 in the Earth's transition zone and in most of the lower mantle. Raman spectroscopy shows the typical bands associated with tetrahedral CO 4 4-groups. DFT-theory based calculations reproduce the experimental Raman spectra and indicate that at least in the athermal limit the phase assemblage of Ca 2 CO 4 + 2SiO 2 is more stable than 2CaSiO 3 + CO 2 at high pressures.

We synthesized two C-S-H compounds from a mixture of carbon and sulfur in hydrogen-C : (H 2 S) 2 H 2 and from sulfur in mixed methane-hydrogen fluids-(CH 4 ) x (H 2 S) (2−x) H 2 at 4 GPa. X-ray synchrotron single-crystal diffraction and Raman spectroscopy have been applied to these samples up to 58 and 143 GPa, respectively. Both samples show a similar Al 2 Cu-type I4/mcm basic symmetry, while the hydrogen subsystem evolves with pressure via variously ordered molecular and extended modifications. The methane-bearing sample lowers symmetry to an orthorhombic Pnma structure after laser heating to 1400 K at 143 GPa. The results suggest that C-S-H compounds are structurally different from a common Im-3m H 3 S.

This paper presents the Domain Auto Finder (DAFi) program and its application to the analysis of single-crystal X-ray diffraction (SC-XRD) data from multiphase mixtures of microcrystalline solids and powders. Superposition of numerous reflections originating from a large number of single-crystal domains of the same and/or different (especially unknown) phases usually precludes the sorting of reflections coming from individual domains, making their automatic indexing impossible. The DAFi algorithm is designed to quickly find subsets of reflections from individual domains in a whole set of SC-XRD data. Further indexing of all found subsets can be easily performed using widely accessible crystallographic packages. As the algorithm neither requires a priori crystallographic information nor is limited by the number of phases or individual domains, DAFi is powerful software to be used for studies of multiphase polycrystalline and microcrystalline (powder) materials. The algorithm is validated by testing on X-ray diffraction data sets obtained from real samples: a multi-mineral basalt rock at ambient conditions and products of the chemical reaction of yttrium and nitrogen in a laser-heated diamond anvil cell at 50 GPa. The high performance of the DAFi algorithm means it can be used for processing SC-XRD data online during experiments at synchrotron facilities.

Non-metal nitrides are an exciting field of chemistry, featuring a significant number of compounds that can possess outstanding material properties. This characteristic relies on maximizing the number of strong covalent bonds, with crosslinked XN6 octahedra frameworks being particularly intriguing. 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 are ultra-incompressible, having a bulk modulus of K0 = 322 GPa for δ-P3N5 and of K0 = 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 high-pressure formed phases.

The search for precursors of luminescent biomarkers is carried out among highly luminescent, stable, and soluble lanthanide p‐substituted fluorobenzoates, which were synthesized and thoroughly characterized. Examination of their crystal structure revealed the dependence of the structure on the lanthanide ion and on the separation method, because of the high acidity of the selected compounds. The brightness of the luminescence of the terbium and europium complexes varies significantly with both absorption and photoluminescence quantum yields (PLQYs), and the latter reaches 62 %.

Charged nitrogen dimers [N2]xare ubiquitous in high-pressure binary metal-nitrogen systems.They are known to possess integer formal charges x varying from one through four. Here, we present the investigation of the binary alkali-and alkaline earth metal-nitrogen systems, Na-N, Ca-N, Sr-N, Ba-N to 70 GPa. We report on compounds- Na3(N2)4, Ca3(N2)4, Sr3(N2)4, and Ba(N2)3-featuring [N2] xunits with paradigm-breaking non-integer charges, x = 0.67, 0.75 and 1.5. The metallic nature of all four compounds is deduced from ab initio calculations. The conduction electrons occupy the π* antibonding orbitals of the [N2] xdimers that results in anion-driven metallicity. Delocalization of these electrons over the π* antibonding states enables the non-integer electron count of the dinitrogen species.Anion-driven metallicity is expected to be found among a variety of compounds with homoatomic anions (e.g., polynitrides, carbides, and oxides), with the conduction electrons playing a decisive role in their properties.

OLEDs based on lanthanide complexes have decisive optical advantages but are hampered by low brightness. Despite efforts to optimize several parameters such as quantum yield and charge carrier mobility, there...

Yttrium nitride, Y5N14, was synthesized by direct reaction between yttrium and nitrogen at ∼50 GPa and ∼2000 K in a laser-heated diamond anvil cell. High-pressure single-crystal X-ray diffraction revealed that the crystal structure of Y5N14 (space group P4/mbm) contains three distinct types of nitrogen dimers. Crystal chemical analysis and ab initio calculations demonstrated that the dimers [N2] x− are crystallographically and chemically nonequivalent and possess distinct noninteger formal charges (x) that make Y5N14 unique among known compounds. Theoretical computations showed that Y5N14 has an anion-driven metallicity, with the filled part of its conduction band formed by nitrogen p-states. The compressibility of Y5N14, determined on decompression down to ∼10 GPa, was found to be uncommonly high for dinitrides containing +3 cations (the bulk modulus K 0 = 137(6) GPa).