Extending the Stability Field of Polymeric Carbon Dioxide Phase V beyond the Earth's Geotherm.

We present a study on the phase stability of dense carbon dioxide (CO_{2}) at extreme pressure-temperature conditions, up to 6200 K within the pressure range 37±9 to 106±17  GPa. The investigations of high-pressure high-temperature in situ x-ray diffraction patterns recorded from laser-heated CO_{2}, as densified in diamond-anvil cells, consistently reproduced the exclusive formation of polymeric tetragonal CO_{2}-V at any condition achieved in repetitive laser-heating cycles. Using well-considered experimental arrangements, which prevent reactions with metal components of the pressure cells, annealing through laser heating was extended individually up to approximately 40 min per cycle in order to keep track of upcoming instabilities and changes with time.

The parisite-(Ce) enigma: challenges in the identification of fluorcarbonate minerals.

A multi-methodological study was conducted in order to provide further insight into the structural and compositional complexity of rare earth element (REE) fluorcarbonates, with particular attention to their correct assignment to a mineral species. Polycrystals from La Pita Mine, Municipality de Maripí, Boyacá Department, Colombia, show syntaxic intergrowth of parisite-(Ce) with röntgenite-(Ce) and a phase which is assigned to (i.e.

2/ Postorthopyroxene γ-LiScGeO, a New Dense High-Pressure Polymorph and Its Direct Transformation from the Structure.

Orthorhombic β-LiScGeO single crystals were compressed hydrostatically up to 10.35 GPa using a diamond anvil cell and investigated in situ by means of X-ray diffraction and Raman spectroscopy. Crystal-structure investigations at ambient conditions and at high pressure show a structural transition from an orthopyroxene-type structure ( ≈ 18.

High-Pressure Behavior of Nickel Sulfate Monohydrate: Isothermal Compressibility, Structural Polymorphism, and Transition Pathway.

Single crystals of synthetic nickel sulfate monohydrate, α-NiSO·HO (space-group symmetry 2/ at ambient conditions), were subject to high-pressure behavior investigations in a diamond-anvil cell up to 10.8 GPa. By means of subtle spectral changes in Raman spectra recorded at 298 K on isothermal compression, two discontinuities were identified at 2.

GZ7 and GZ8 - Two Zircon Reference Materials for SIMS U-Pb Geochronology.

Here, we document a detailed characterisation of two zircon gemstones, GZ7 and GZ8. Both stones had the same mass at 19.2 carats (3.

Crystalline polymeric carbon dioxide stable at megabar pressures.

Carbon dioxide is a widespread simple molecule in the Universe. In spite of its simplicity it has a very complex phase diagram, forming both amorphous and crystalline extended phases above 40 GPa. The stability range and nature of these phases are still debated, especially in view of their possible role within the deep carbon cycle.

Evolution of the α-BaMg(CO) low-temperature superstructure and the tricritical nature of its α-β phase transition.

The crystal structure of the synthetic double carbonate norsethite [BaMg(CO)] has been reinvestigated using X-ray diffraction data within the temperature range 100-500 K using a high-sensitivity PILATUS pixel detector. The previously assumed positional shift of the crystallographically unique oxygen atom is confirmed. The shift is associated with a coupled rotation of symmetry-equivalent carbonate groups.