Dissociation of Liquid Silica at High Pressures and Temperatures

Hicks, D. G.; Boehly, T. R.; Eggert, J. H.; Miller, James E.; Celliers, P. M.; Collins, G. W.

doi:10.1103/physrevlett.97.025502

Cited by 187 publications

(221 citation statements)

References 22 publications

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“…At 8000 K and 56 GPa, we find σ ion ≈ 2.5 × 10 3 S/m and σ el ≈ 1.0 × 10 5 S/m, the electronic density of states displaying no band gap [31]. Our result σ ≈ 10 5 S/m is similar to experimentally based estimates of the conductivity of other liquid planetary materials, such as MgO (>10 4 S/m) [6], SiO 2 (10 4 to 10 5 S/m) [56], and MgSiO 3 (>10 5 S/m) [57], noting though that some of these experiments were performed at higher temperatures and pressures [6,57]. The predicted (nearly) metallic conductivity of liquid (Mg,Fe)O raises the possibility that as a component of an early basal magma ocean, the material may have functioned to give rise to a magnetic field on Earth long before the onset of the present core dynamo mechanism [58].…”

Section: E Electrical Conductivitysupporting

confidence: 76%

Spin crossover in liquid (Mg,Fe)O at extreme conditions

Holmström

Stixrude

2016

Phys. Rev. B

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We use first-principles free-energy calculations to predict a pressure-induced spin crossover in the liquid planetary material (Mg,Fe)O, whereby the magnetic moments of Fe ions vanish gradually over a range of hundreds of GPa. Because electronic entropy strongly favors the nonmagnetic low-spin state of Fe, the crossover has a negative effective Clapeyron slope, in stark contrast to the crystalline counterpart of this transition-metal oxide. Diffusivity of liquid (Mg,Fe)O is similar to that of MgO, displaying a weak dependence on element and spin state. Fe-O and Mg-O coordination increases from approximately 4 to 7 as pressure goes from 0 to 200 GPa. We find partitioning of Fe to induce a density inversion between the crystal and melt, implying separation of a basal magma ocean from a surficial one in the early Earth. The spin crossover induces an anomaly into the density contrast, and the oppositely signed Clapeyron slopes for the crossover in the liquid and crystalline phases imply that the solid-liquid transition induces a spin transition in (Mg,Fe)O.

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Section: E Electrical Conductivitysupporting

confidence: 76%

Spin crossover in liquid (Mg,Fe)O at extreme conditions

Holmström

Stixrude

2016

Phys. Rev. B

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“…Scaling of the experimental results to the predicted giant impact conditions suggests complete turbulent mixing of the metal and silicate of the impactor material in just a few hours. The experiments also suggest that the post-giant-impact (Hicks et al 2006) and the approximate pressure and temperature conditions of the core-mantle boundary (CMB) in the Earth today. Also shown are P-T conditions for our experiments Remo et al 2007Remo et al , 2008; symbols with error bars) on melting and homogenization of Fe-metal and dunite mixtures.…”

Section: Formation Of the Earth And The Moonmentioning

confidence: 99%

Isotopes as clues to the origin and earliest differentiation history of the Earth

Jacobsen

Ranen

Petaev

et al. 2008

Phil. Trans. R. Soc. A.

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Measurable variations in 182 W/ 183 W, 142 Nd/ 144 Nd, 129 Xe/ 130 Xe and 136 Xe Pu / 130 Xe in the Earth and meteorites provide a record of accretion and formation of the core, early crust and atmosphere. These variations are due to the decay of the now extinct nuclides 182 Hf, 146 Sm, 129 I and 244 Pu. The l82 Hf– 182 W system is the best accretion and core-formation chronometer, which yields a mean time of Earth's formation of 10 Myr, and a total time scale of 30 Myr. New laser shock data at conditions comparable with those in the Earth's deep mantle subsequent to the giant Moon-forming impact suggest that metal–silicate equilibration was rapid enough for the Hf–W chronometer to reliably record this time scale. The coupled 146 Sm– 147 Sm chronometer is the best system for determining the initial silicate differentiation (magma ocean crystallization and proto-crust formation), which took place at ca 4.47 Ga or perhaps even earlier. The presence of a large 129 Xe excess in the deep Earth is consistent with a very early atmosphere formation (as early as 30 Myr); however, the interpretation is complicated by the fact that most of the atmospheric Xe may be from a volatile-rich late veneer.

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“…The correction to this approximation can then be estimated by using a detailed equation of state model for quartz. For all of our experiments the shocked quartz was strong enough to transform it into a conducting dissociated fluid [15]. We have used a Mie-Gruneisen model with Γ = 0.66, valid in this dense fluid domain, to generate a correction to the reflected shock were made with it.…”

Section: Impedance Matching For Eos Determinationmentioning

confidence: 99%

Creating the Core Conditions of Extra-solar and Solar Giant Planets

Celliers¹,

Eggert²,

Collins³

et al. 2007

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Materials can be experimentally characterized at high pressures and densities by sending a laser-induced shock wave through a sample that is pre-compressed inside a diamond-anvil cell. This combination of static-and dynamic-compression methods has been experimentally demonstrated, and ultimately provides access to the 10-100 TPa (0.1-1 Gbar) pressure range that is relevant to planetary science. We report on dynamical measurements of the high pressure compressibility of helium, hydrogen and helium/hydrogen mixtures up to 230 GPa by combining laser shocks and static compression in diamond anvil cells. The initial density of samples in these precompressed targets has been varied by a factor of 3. The measurements on the principal He Hugoniot, i.e with the initial density of cryo-helium, is extended above 100 GPa and a maximum of compression ratio of greater than 5-fold of the initial density is observed. Also, a strong decrease in compressibility is observed by increasing the initial density. A similar data set has been produced for precompressed H 2 and a mixture of He and H 2 .

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Dissociation of Liquid Silica at High Pressures and Temperatures

Cited by 187 publications

References 22 publications

Spin crossover in liquid (Mg,Fe)O at extreme conditions

Spin crossover in liquid (Mg,Fe)O at extreme conditions

Isotopes as clues to the origin and earliest differentiation history of the Earth

Creating the Core Conditions of Extra-solar and Solar Giant Planets

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