Ramp Compression of Germanium Dioxide to Extreme Conditions: Phase Transitions in an SiO 2 Analog
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75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Engineering topics
Wicks, J. K.
Publications and source records attributed to Wicks, J. K..
Structure and density of silicon carbide to 1.5 TPa and implications for extrasolar planets
There has been considerable recent interest in the high-pressure behavior of silicon carbide, a potential major constituent of carbon-rich exoplanets. In this work, the atomic-level structure of SiC was determined through in situ X-ray diffraction under laser-driven ramp compression up to 1.5 TPa; stresses more than seven times greater than previous static and shock data. Here we show that the B1-type structure persists over this stress range and we have constrained its equation of state (EOS). Using this data we have determined the first experimentally based mass-radius curves for a hypothetical pure SiC planet. Interior structure models are constructed for planets consisting of a SiC-rich mantle and iron-rich core. Carbide planets are found to be ~10% less dense than corresponding terrestrial planets.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Recovery of a high-pressure phase formed under laser-driven compression
The recovery of metastable structures formed at high pressure has been a long-standing goal in the field of condensed matter physics. While laser-driven compression has been used as a method to generate novel structures at high pressure, to date no high-pressure phases have been quenched to ambient conditions. Here we demonstrate, using in situ x-ray diffraction and recovery methods, the successful quench of a high-pressure phase which was formed under laser-driven shock compression. We show that tailoring the pressure release path from a shock-compressed state to eliminate sample spall, and therefore excess heating, increases the recovery yield of the high-pressure ω phase of zirconium from 0% to 48%. Our results have important implications for the quenchability of novel phases of matter demonstrated to occur at extreme pressures using nanosecond laser-driven compression.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Coordination changes in liquid tin under shock compression determined using in situ femtosecond x-ray diffraction
Little is known regarding the liquid structure of materials compressed to extreme conditions, and even less is known about liquid structures undergoing rapid compression on nanosecond timescales. Here, we report on liquid structure factor and radial distribution function measurements of tin shock compressed to 84(19) GPa. High-quality, femtosecond x-ray diffraction measurements at the Linac Coherent Light Source were used to extract the liquid diffuse scattering signal. From the radial distribution function, we find that the structural evolution of the liquid with increasing pressure mimics the evolution of the solid phase. With increasing pressure, we find that the liquid structure evolves from a complex structure, with a low coordination number, to a simple liquid structure with a coordination number of ~12. We provide a pathway for future experiments to study liquids at elevated pressures using high-energy lasers to shock compress materials beyond the reach of static diamond anvil cell techniques.
X-ray diffraction↗
I n s i t u observation of a phase transition in silicon carbide under shock compression using pulsed x-ray diffraction
The behavior of silicon carbide (SiC) under shock compression is of interest due to its applications as a high-strength ceramic and for general understanding of shock-induced polymorphism. Here we use the Matter in Extreme Conditions beamline of the Linac Coherent Light Source to carry out a series of time-resolved pump-probe x-ray diffraction measurements on SiC laser-shocked to as high as 206 GPa. Experiments on single crystals and polycrystals of different polytypes show a transformation from a low-pressure tetrahedral phase to the high-pressure rocksalt-type (B1) structure. We directly observe coexistence of the low- and high-pressure phases in a mixed-phase region and complete transformation to the B1 phase above 200 GPa. The densities measured by x-ray diffraction are in agreement with both continuum gas-gun studies and a theoretical B1 Hugoniot derived from static-compression data. Time-resolved measurements during shock loading and release reveal a large hysteresis upon unloading, with the B1 phase retained to as low as 5 GPa. The sample eventually reverts to a mixture of polytypes of the low-pressure phase at late times. Our study demonstrates that x-ray diffraction is an effective means to characterize the time-dependent structural response of materials undergoing shock-induced phase transformations at megabar pressures.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗