Daniel Sneed
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View article: Raman scattering of rhenium for secondary pressure calibration
Raman scattering of rhenium for secondary pressure calibration Open
With the increasing number of 100 s GPa experiments in the diamond anvil cell (DAC), improved accuracy in secondary pressure calibrations to extreme pressures is essential. The rhenium equation of state has been proposed as a pressure cali…
View article: X-ray phase contrast imaging and diffraction in the laser-heated diamond anvil cell: A case study on the high-pressure melting of Pt
X-ray phase contrast imaging and diffraction in the laser-heated diamond anvil cell: A case study on the high-pressure melting of Pt Open
Melting temperatures of materials at high-pressure are one of the key physical properties that can be measured. However, large discrepancies in high-pressure melt lines exist between different experimental and theoretical approaches. In th…
View article: MHz free electron laser x-ray diffraction and modeling of pulsed laser heated diamond anvil cell
MHz free electron laser x-ray diffraction and modeling of pulsed laser heated diamond anvil cell Open
A new diamond anvil cell experimental approach has been implemented at the European x-ray Free Electron Laser, combining pulsed laser heating with MHz x-ray diffraction. Here, we use this setup to determine liquidus temperatures under extr…
View article: Charge Order Evolution of Superconducting BaNi2As2 Under High Pressure
Charge Order Evolution of Superconducting BaNi2As2 Under High Pressure Open
BaNi$_2$As$_2$, a non-magnetic superconductor counterpart to BaFe$_2$As$_2$, has been shown to develop nematic order, multiple charge orders, and a dramatic six-fold enhancement of superconductivity via isovalent chemical substitution of S…
View article: A MHz X-ray diffraction set-up for dynamic compression experiments in the diamond anvil cell
A MHz X-ray diffraction set-up for dynamic compression experiments in the diamond anvil cell Open
An experimental platform for dynamic diamond anvil cell (dDAC) research has been developed at the High Energy Density (HED) Instrument at the European X-ray Free Electron Laser (European XFEL). Advantage was taken of the high repetition ra…
View article: Laser-melting Bismuth - A case study for X-ray imaging at high pressure and temperature
Laser-melting Bismuth - A case study for X-ray imaging at high pressure and temperature Open
Our understanding on how opaque materials respond to extreme compression and high temperatures heavily relies on x-ray techniques. While X-ray diffraction is a powerful approach, some properties such as viscosity are experimentally not acc…
View article: CO2 laser heating system for <i>in situ</i> radial x-ray absorption at 16-BM-D at the Advanced Photon Source
CO2 laser heating system for <i>in situ</i> radial x-ray absorption at 16-BM-D at the Advanced Photon Source Open
We present a portable CO2 laser heating system for in situ x-ray absorption spectroscopy (XAS) studies at 16-BM-D (High Pressure Collaborative Access Team, Advanced Photon Source, Argonne National Laboratory). Back scattering optical measu…
View article: High-pressure structural systematics of dysprosium metal compressed in a neon pressure medium to 182 GPa
High-pressure structural systematics of dysprosium metal compressed in a neon pressure medium to 182 GPa Open
Here we present an experimental and theoretical study of dysprosium metal compressed in the soft pressure transmitting medium Ne up to 182 and 300 GPa, respectively. Angle-dispersive x-ray powder diffraction data from each of the high-pres…
View article: Simultaneous imaging and diffraction in the dynamic diamond anvil cell
Simultaneous imaging and diffraction in the dynamic diamond anvil cell Open
The ability to visualize a sample undergoing a pressure-induced phase transition allows for the determination of kinetic parameters, such as the nucleation and growth rates of the high-pressure phase. For samples that are opaque to visible…
View article: Systematic structural study in praseodymium compressed in a neon pressure medium up to 185 GPa
Systematic structural study in praseodymium compressed in a neon pressure medium up to 185 GPa Open
Angle-dispersive x-ray powder diffraction experiments have been performed on praseodymium metal compressed in a soft pressure-transmitting medium at ambient temperature up to 185 GPa. We observe the previously reported high-pressure struct…
View article: High pressure stability of β-Zr: no evidence for isostructural phase transitions
High pressure stability of β-Zr: no evidence for isostructural phase transitions Open
Isostructural transitions have been reported to occur in several pure elements; however, most of these have been disproven. Zr is one of those elements which remains controversial with two reports of an isostructural bcc-to-bcc transition …
View article: Pressure Driven Electronic Band Gap Engineering in Tin(IV)-O,N Compounds
Pressure Driven Electronic Band Gap Engineering in Tin(IV)-O,N Compounds Open
The intrinsic link between long-range order, coordination geometry, and the electronic properties of a system must be understood in order to tailor function-specific materials. Although material properties are typically tailored using chem…
View article: Forcing Cesium into Higher Oxidation States via Useful Hard X-ray Induced Chemistry at Extreme Conditions
Forcing Cesium into Higher Oxidation States via Useful Hard X-ray Induced Chemistry at Extreme Conditions Open
Recent theoretical work published in Nature Chemistry postulates the existence of cesium in high oxidation states when bonding with fluorine. It is thus predicted to behave as a p-block element (such as xenon) at pressures above 5 GPa. At …
View article: Anomalous Conductivity in the Rutile Structure Driven by Local Disorder
Anomalous Conductivity in the Rutile Structure Driven by Local Disorder Open
Many rutile-type materials are characterized by a softness in shear with pressure which is coupled to a Raman-active librational motion. Combining direct studies of anion positions in SnO2 with measurements of its electronic properties, we…
View article: Pressure‐Tuneable Visible‐Range Band Gap in the Ionic Spinel Tin Nitride
Pressure‐Tuneable Visible‐Range Band Gap in the Ionic Spinel Tin Nitride Open
The application of pressure allows systematic tuning of the charge density of a material cleanly, that is, without changes to the chemical composition via dopants, and exploratory high‐pressure experiments can inform the design of bulk syn…
View article: Pressure‐Tuneable Visible‐Range Band Gap in the Ionic Spinel Tin Nitride
Pressure‐Tuneable Visible‐Range Band Gap in the Ionic Spinel Tin Nitride Open
The application of pressure allows systematic tuning of the charge density of a material cleanly, that is, without changes to the chemical composition via dopants, and exploratory high‐pressure experiments can inform the design of bulk syn…
View article: Forcing Cesium into Higher Oxidation States Using Useful hard x-ray Induced Chemistry under High Pressure
Forcing Cesium into Higher Oxidation States Using Useful hard x-ray Induced Chemistry under High Pressure Open
This paper discusses our attempt to synthesize higher oxidation forms of cesium fluoride by pressurizing cesium fluoride in a fluorine-rich environment created via the x-ray decomposition of potassium tetrafluoroborate. This was done in or…
View article: High-pressure equation of state of cesium fluoride to 120 GPa
High-pressure equation of state of cesium fluoride to 120 GPa Open
We have performed a high pressure synchrotron X-ray diffraction study of the ionic salt, cesium fluoride (CsF), up to 120 GPa. We observed the B1 → B2 phase transition near 5 GPa as previously reported. Beyond this pressure, no phase trans…
View article: High-pressure equation of state of cesium fluoride to 120 GPa
High-pressure equation of state of cesium fluoride to 120 GPa Open
We have performed a high pressure synchrotron X-ray diffraction study of the ionic salt, cesium fluoride (CsF), up to 120 GPa. We observed the B1 → B2 phase transition near 5 GPa as previously reported. Beyond this pressure, no phase trans…
View article: A novel synthesis of polymeric CO via useful hard X-ray photochemistry
A novel synthesis of polymeric CO via useful hard X-ray photochemistry Open
We report on the synchrotron hard X-ray-induced decomposition of strontium oxalate (SrC2O4) pressurized to 7 GPa inside a diamond anvil cell (DAC). After some 4 h of irradiation in a white X-ray synchrotron beam, a dark reddish/brown regio…
View article: Hexafluorobenzene under Extreme Conditions
Hexafluorobenzene under Extreme Conditions Open
We report the results from three high pressure experiments on hexafluorobenzene (C6F6). In the first experiment, Raman spectra were recorded up to 34.4 GPa. A phase transition from I → II was observed near 2 GPa. Near 8.8 GPa, a phase tran…