120 research outputs found
Melting and metallization of silica in the cores of gas giants, ice giants and super Earths
The physical state and properties of silicates at conditions encountered in
the cores of gas giants, ice giants and of Earth like exoplanets now discovered
with masses up to several times the mass of the Earth remains mostly unknown.
Here, we report on theoretical predictions of the properties of silica,
SiO, up to 4 TPa and about 20,000K using first principle molecular dynamics
simulations based on density functional theory. For conditions found in the
Super-Earths and in ice giants, we show that silica remains a poor electrical
conductor up to 10 Mbar due to an increase in the Si-O coordination with
pressure. For Jupiter and Saturn cores, we find that MgSiO silicate has not
only dissociated into MgO and SiO, as shown in previous studies, but that
these two phases have likely differentiated to lead to a core made of liquid
SiO and solid (Mg,Fe)O.Comment: 5 pages, 4 figure
Decaying shock studies of phase transitions in MgOSiO2 systems: implications for the Super-Earths interiors
We report an experimental study of the phase diagrams of periclase (MgO),
enstatite (MgSiO3) and forsterite (Mg2SiO4) at high pressures. We investigated
with laser driven decaying shocks the pressure/temperature curves of MgO,
MgSiO3 and Mg2SiO4 between 0.2-1.2 TPa, 0.12-0.5 TPa and 0.2-0.85 TPa
respectively. A melting signature has been observed in MgO at 0.47 TPa and 9860
K, while no phase changes were observed neither in MgSiO3 nor in Mg2SiO4. An
increasing of reflectivity of MgO, MgSiO3 and Mg2SiO4 liquids have been
detected at 0.55 TPa -12 760 K, 0.15 TPa - 7540 K, 0.2 TPa - 5800 K,
respectively. In contrast to SiO2, melting and metallization of these compounds
do not coincide implying the presence of poor electrically conducting liquids
close to the melting lines. This has important implications for the generation
of dynamos in Super-earths mantles
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Laser-driven shock experiments in pre-compressed water: Implications for magnetic field generation in Icy Giant planets
Laser-driven shock compression of pre-compressed water (up to 1 GPa precompression) produces high-pressure, -temperature conditions in the water inducing two optical phenomena: opacity and reflectivity in the initially transparent water. The onset of reflectivity at infrared wavelengths can be interpreted as a semi-conductor to electronic conductor transition in water and is found at pressures above {approx}130 GPa for single-shocked samples pre-compressed to 1 GPa. This electronic conduction provides an additional contribution to the conductivity required for magnetic field generation in Icy Giant planets like Uranus and Neptune
Zr-based bulk metallic glasses equation of state under laser shock compression and spall strength
International audienc
Zr-based bulk metallic glasses equation of state under laser shock compression and spall strength
International audienc
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