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The article examines material liquid structure when compressed to 84(19) gigapascals (GPa). It reports on the radial distribution function and liquid structure function of tin that undergoes shock compression using femtosecond x-ray diffraction to study liquid diffuse scattering signals.It comments that the structural evolution of the liquid tin under increasing pressure mimicked the evolution of the solid phase and evolved into a simple liquid structure with a coordination number around 12.

The compressibility of fluid deuterium up to several Mbar has been probed using laser-driven shock waves reflected from a quartz anvil. Combining high-precision (∼1%) shock velocity measurements with the double-shock technique, where differences in equation of state (EOS) models are magnified, has allowed better discrimination between theoretical predictions in the second-shock regime. Double-shock results are in agreement with the stiffer EOS models—which exhibit roughly fourfold single-shock compression—for initial shocks up to 1 Mbar and above 2 Mbar, but diverge from these predictions in between. Softer EOS models—which exhibit sixfold single-shock compression at 1 Mbar—overestimate the reshock pressure for the entire range under study. [ABSTRACT FROM AUTHOR]

The optical reflectance of a strong shock front in water increases continuously with pressure above 100 GPa and saturates at ∼45% reflectance above 250 GPa. This is the first evidence of electronic conduction in high pressure water. In addition, the water Hugoniot equation of state up to 790 GPa (7.9 Mbar) is determined from shock velocity measurements made by detecting the Doppler shift of reflected light. From a fit to the reflectance data we find that an electronic mobility gap ∼2.5 eV controls thermal activation of electronic carriers at pressures in the range of 100–150 GPa. This suggests that electronic conduction contributes significantly to the total conductivity along the Neptune isentrope above 150 GPa. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Laser-driven shock compression experiments reveal the presence of a phase transition in MgSi03 over the pressure-temperature range 300-400 GPa and 10000-16 000 K, with a positive Clapeyron slope and a volume change of ∼6.3 (± 2.0) percent. The observations are most readily interpreted as an abrupt liquid-liquid transition in a silicate composition representative of terrestrial planetary mantles, implying potentially significant consequences for the thermal-chemical evolution of extrasolar planetary interiors. In addition, the present results extend the Hugoniot equation of state of MgSi03 single crystal and glass to 950 GPa. [ABSTRACT FROM AUTHOR]

Deep inside planets, extreme density, pressure, and temperature strongly modify the properties of the constituent materials. In particular, how much heat solids can sustain before melting under pressure is key to determining a planet's internal structure and evolution. We report laser-driven shock experiments on fused silica, α-quartz, and stishovite yielding equation-of-state and electronic conductivity data at unprecedented conditions and showing that the melting temperature of SiO2 rises to 8300 K at a pressure of 500 gigapascals, comparable to the core-mantle boundary conditions for a 5-Earth mass super-Earth. We show that mantle silicates and core metal have comparable melting temperatures above 500 to 700 gigapascals, which could favor long-lived magma oceans for large terrestrial planets with implications for planetary magnetic-field generation in silicate magma layers deep inside such planets. [ABSTRACT FROM AUTHOR]