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RECENT PUBLICATIONS

GSECARS Benchtop SEM

GSECARS now has a JEOL Neoscope 6000PLUS scanning electron microscope available to GSECARS and APS users in support of beamline experiments. Click here for more info.

GSECARS Laser Lab

Users interested in using the Raman System or Micromanipulator,
Click here for more info. 

Science Highlights

Ultrahigh-pressure isostructural electronic transitions in hydrogen

High-pressure transitions are thought to modify hydrogen molecules to a molecular metallic solid and finally to an atomic metal, which is predicted to have exotic physical properties and the topology of a two-component (electron and proton) superconducting superfluid condensate. Therefore, understanding such transitions remains an important objective in condensed matter physics. However, measurements of the crystal structure of solid hydrogen, which provides crucial information about the metallization of hydrogen under compression, are lacking for most high-pressure phases, owing to the considerable technical challenges involved in X-ray and neutron diffraction measurements under extreme conditions. Here we present a single-crystal X-ray diffraction study of solid hydrogen at pressures of up to 254 gigapascals that reveals the crystallographic nature of the transitions from phase I to phases III and IV.  Click 

Pressure-Induced Superconductivity and Flattened Se₆ Rings in the Wide Band Gap Semiconductor Cu₂I₂Se₆

The two major classes of unconventional superconductors, cuprates and Fe-based superconductors, have magnetic parent compounds, are layered, and generally feature square-lattice symmetry. We report the discovery of pressure-induced superconductivity in a nonmagnetic and wide band gap 1.95 eV semiconductor, Cu2I2Se6, with a unique anisotropic structure composed of two types of distinct molecules: Se6 rings and Cu2I2 dimers, which are linked in a three-dimensional framework. Click 

An upgraded and integrated large-volume high-pressure facility at the GeoSoilEnviroCARS bending magnet beamline of the Advanced Photon Source

The multi-anvil, large-volume high-pressure facility at the bending magnet beamline (13-BM-D) runs a unique setup permitting an unusually wide range of high-pressure and high-temperature experiments combined with X-rays and other in-situ probing techniques.  Here we provide a detailed description of the current large-volume press (LVP) setup at 13-BM-D, including hardware, software, and all experimental capabilities. Click 

Phase transitions beyond post-perovskite in NaMgF₃ to 160 GPa

The high-pressure behavior of NaMgF₃ is of interest due to its role as a low-pressure analog for phase transitions in the MgSiO₃ system. In this work, we have used the diamond anvil cell and synchrotron X-ray diffraction techniques to study structural transitions in NaMgF₃ to 1.6 Mbars. Our work has identified a sequence of high-pressure phases beyond post-perovskite in this ABX₃ system.  Click 

Depositional and diagenetic constraints on the abundance and spatial variability of carbonate-associated sulfate

Here, we have combined X-ray Absorption Near Edge Structure (XANES) spectroscopy and μ-X-ray Fluorescence (μ-XRF) imaging to map the speciation and abundance of sulfur in carbonate petrographic thin sections in Upper Ordovician carbonates from Anticosti Island, Canada and early Silurian carbonates from Gotland, Sweden, across multiple depositional facies.  The detection and characterization of both inorganic sulfur and organic sulfur compounds provides a platform to understand early processes of biomineralization. This approach will broaden our understanding of the source of inorganically bound sulfate in ancient carbonates, as well as the effect of depositional setting and diagenesis on CAS incorporation, (re)mobilization, and ultimate abundance in sedimentary carbonates. Click

Solubility and speciation of iron in hydrothermal fluids

Here, we conducted hydrothermal diamond-anvil cell experiments using synchrotron-radiation micro-XRF and XANES analyses as well as Raman spectroscopy, in situ at hydrothermal temperatures and pressures, to characterize the solubility and speciation of iron in fluids buffered by a variety of mineral assemblages. Click

Immiscibility between two rutile phases in the GeO2–TiO2 system and application as a temperature sensor in high-pressure experiments

The system GeO2–TiO2 was studied experimentally at high pressure and temperature to measure the miscibility of the two components and to test its applicability as a temperature sensor in high-pressure experiments. Click