Learn More
The reactivity of xenon with terrestrial oxides was investigated by in situ synchrotron x-ray diffraction. At high temperature (T > 500 kelvin), some silicon was reduced, and the pressure stability of quartz was expanded, attesting to the substitution of some xenon for silicon. When the quartz was quenched, xenon diffused out and only a few weight percent(More)
Sodium exhibits a pronounced minimum of the melting temperature at approximately 118 gigapascals and 300 kelvin. Using single-crystal high-pressure diffraction techniques, we found that the minimum of the sodium melting curve is associated with a concentration of seven different crystalline phases. Slight changes in pressure and/or temperature induce(More)
The triple bond of diatomic nitrogen has among the greatest binding energies of any molecule. At low temperatures and pressures, nitrogen forms a molecular crystal in which these strong bonds co-exist with weak van der Waals interactions between molecules, producing an insulator with a large band gap. As the pressure is raised on molecular crystals,(More)
Silane (SiH 4) is found to (partially) decompose at pressures above 50 GPa at room temperature into pure Si and H 2. The released hydrogen reacts with surrounding metals in the diamond anvil cell to form metal hydrides. A formation of rhenium hydride is observed after the decomposition of silane. From the data of a previous experimental report (Eremets et(More)
Highly sensitive magnetic susceptibility techniques were used to measure the superconducting transition temperatures in S up to 231(±5) GPa. S transforms to a superconductor with Tc of 10 K and has a discontinuity in Tc dependence at 160 GPa corresponding to bco to β-Po phase transition. Above this pressure Tc in S has a maximum reaching about 17.3(±0.5) K(More)
Almost 80 years ago it was predicted that, under sufficient compression, the H-H bond in molecular hydrogen (H2) would break, forming a new, atomic, metallic, solid state of hydrogen. Reaching this predicted state experimentally has been one of the principal goals in high-pressure research for the past 30 years. Here, using in situ high-pressure Raman(More)
Molecular nitrogen exhibits one of the strongest known interatomic bonds, while xenon possesses a closed-shell electronic structure: a direct consequence of which renders both chemically unreactive. Through a series of optical spectroscopy and x-ray diffraction experiments, we demonstrate the formation of a novel van der Waals compound formed from binary(More)
Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the(More)
Foreword This PhD project was funded by an Internationalisation Grant from the Dan-ish Research Training Council (FUR). The funding covered fees, salary and travel expenses for attending conferences and for annual visits to the Geological Institute , University of Copenhagen which administrated the grant. With the grant followed an obligation to stay in(More)
The melting curve of H(2)O has been measured by in situ Raman spectroscopy in an externally heated diamond anvil cell up to 22 GPa and 900 K. The Raman-active OH-stretching bands and the translational modes of H(2)O as well as optical observations are used to directly and reliably detect melting in ice VII. The observed melting temperatures are higher than(More)
  • 1