We determined the metal/silicate partition coefficients of hydrogen and carbon, DH and DC, simultaneously under typical conditions of Earth's core formation. Experiments demonstrate that both DH and DC diminish in the presence of carbon and hydrogen, respectively, indicating their strong interactions in liquid metal. With these partitioning data, we investigated the core and bulk Earth abundances of hydrogen and carbon based on core formation scenarios that are compatible with the bulk silicate Earth composition and the mass fraction and density deficit of the core. The results of the single-stage core formation modelling are markedly different from those using DH and DC individually determined in earlier experiments, indicating that the Earth building blocks do not match enstatite chondrites in water abundance and require contributions by carbonaceous chondrites. The multi-stage core formation models combined with an Earth accretion scenario accounting for isotopic composition show 0.18-0.49 wt

We report the formations of fcc and distorted hcp iron-helium compounds with x in FeHex up to 0.13 and 0.48, respectively, based on experiments at 5-54 GPa and 1000-2820 K. Upon releasing pressure under room temperature, these fcc and distorted hcp FeHex were still observed by XRD and SIMS measurements. Our first-principles calculations indicate that fcc and hcp FeHex, with helium atoms occupying the tetrahedral and trigonal-planar interstitial sites (instead of the octahedral sites), are dynamically stable throughout 0-50 GPa. These results support that the Earth's core can be a large reservoir of primordial 3He.

Hydrogen and carbon concentrations in the Earth's core are yet known. Here we determined their metal/silicate partition coefficients (D) simultaneously under typical conditions of core formation and found that DH and DC diminish in the presence of carbon and hydrogen, respectively, because of strong interactions between hydrogen and carbon in liquid metal, being markedly different from those separately examined in earlier experiments. With these partitioning data, we investigated the core and bulk Earth abundances of hydrogen and carbon based on core formation scenarios that are compatible with the bulk silicate Earth composition and the mass fraction and density of the core. The modelling results indicate that the Earth building blocks do not match enstatite chondrites in water abundance but require contributions by carbonaceous chondrites. The multi-stage core formation models combined with an Earth accretion scenario accounting for isotopic composition show 0.18-0.49 wt% H and 0.19-1.37 wt% C in the core, leading to 0.53-1.40 wt% H2O (present as H in the core) and 0.07-0.44 wt% C in the bulk Earth. Our modelling also demonstrates that up to 53% and 72% of Earth's water (hydrogen) and carbon, respectively, could have been derived from non-carbonaceous chondritic materials.

(Mg,Fe)O ferropericlase-magnesiow & uuml;stite has been proposed to host the majority of Earth's sodium, but the mechanism and capacity for incorporating the alkali cation remain unclear. In this work, experiments in the laser-heated diamond anvil cell and first-principles calculations determine the solubility of sodium and favorability of sodium incorporation in iron-rich magnesiow & uuml;stite relative to (Mg,Fe)SiO3 bridgmanite. Reaction of Mg/(Mg + Fe) (Mg#) 55 and 28 olivine with NaCl at 33-128 GPa and 1600-3000 K produces iron-rich magnesiow & uuml;stite containing several percent sodium, while iron-rich bridgmanite contains little to no detectable sodium. In sodium-saturated magnesiow & uuml;stite, sodium number [Na/(Na + Mg + Fe)] is 2-5 atomic percent at pressures below 60 GPa and drastically increases to 10-20 atomic percent at deep lower mantle pressures. For these two compositions, there is no significant dependence of the results on Mg#. Our calculations not only show consistent results with experiments but further indicate that such an increase in solubility and partitioning of Na into magnesiow & uuml;stite is driven by the spin transition in iron. These results provide fundamental constraints on the crystal chemistry of sodium at lower-mantle conditions. If the sodium capacity of (Mg,Fe)O is not strongly dependent on Mg#, (Mg,Fe)O in the lower mantle may have the capacity to store the entire sodium budget of the Earth. Sodium is among the most abundant elements on the Earth, but where it can be stored in the Earth's largest layer, the lower mantle, has not been understood. Whether sodium dissolves into the most common minerals in the mantle affects the interpretation of the Earth's composition and structure. This study uses experiments and computer simulations of reactions of sodium with the two most common minerals in the lower mantle to determine how much sodium can be dissolved in the mantle. Both methods show that enough sodium can dissolve into magnesium-iron oxide, called ferropericlase or magnesiow & uuml;stite, to store all of the Earth's sodium budget. The amount of sodium that dissolves into this mineral increases with depth in the Earth because of a change in the arrangement of electrons around iron, which takes part in the chemical reaction with sodium. Experiments show that sodium strongly partitions to (Mg,Fe)O magnesiow & uuml;stite and is not incorporated in bridgmanite Sodium is soluble in iron-rich (Mg,Fe)O in the deep lower mantle at multiple percent level First-principle calculations show that spin transition in (Mg,Fe)O drives a pressure-driven increase in sodium solubility

Fe-bearing MgO [(Mg1-xFex)O] is considered a major constituent of terrestrial exoplanets. Crystallizing in the B1 structure in the Earth's lower mantle, (Mg1-xFex)O undergoes a high-spin (S = 2) to low-spin (S = 0) transition at ∼45 GPa, accompanied by anomalous changes of this mineral's physical properties, while the intermediate-spin (S = 1) state has not been observed. In this work, we investigate (Mg1-xFex)O (x ≤ 0.25) up to 1.8 TPa via first-principles calculations. Our calculations indicate that (Mg1-xFex)O undergoes a simultaneous structural and spin transition at ∼0.6 TPa, from the B1 phase low-spin state to the B2 phase intermediate-spin state, with Fe's total electron spin S re-emerging from 0 to 1 at ultrahigh pressure. Upon further compression, an intermediate-to-low spin transition occurs in the B2 phase. Depending on the Fe concentration (x), metal-insulator transition and rhombohedral distortions can also occur in the B2 phase. These results suggest that Fe and spin transition may affect planetary interiors over a vast pressure range.

Carbon dioxide is commonly found in terrestrial planets and its thermal property is relevant to the dynamics and evolution of those terrestrial planets. In this work, we combine time‐domain thermoreflectance measurements and first‐principles calculations to determine the thermal conductivity of CO2 up to 70 GPa at room temperature. Our results show that the thermal conductivity of liquid CO2 is ∼0.22 W m−1 K−1 at 0.3–0.5 GPa and increases to ∼0.28 W m−1 K−1 when the liquid CO2 transforms into molecular solid phase I (dry ice). Upon further compression, the mean value of thermal conductivity of phase I increases to 1.4–2.1 W m−1 K−1 at ∼10 GPa and then slightly drops across the phase I‐III boundary. Phase III exhibits a gentle increase of thermal conductivity with pressure and reaches to a maximum value of ∼4 W m−1 K−1 at ∼45 GPa, but shows an abrupt drop when transforming into a non‐molecular amorphous solid. The pressure evolution of CO2 thermal conductivity across different phases may have significant implications for the heat flow and temperature distribution in the interiors of planets and moons containing CO2.

Methane is a primary component of the “ice” layers in icy bodies whose thermal transport properties and velocity‐density profiles are essential to understanding their unique geodynamic and physiochemical phenomena. We present experimental measurements of methane's thermal conductivity and compressional velocity to 25.1 and 45.1 GPa, respectively, at room temperature, and theoretical calculations of its equation of state, velocity, and heat capacity up to 100 GPa and 1200 K. Overall, these properties change smoothly with pressure and are generally unaffected by the imposed atomic structure; though we observe a discrete spike in conductivity near the I‐A phase boundary. We cross‐plot the thermal conductivity and compressional velocity with density for the primary “ice” constituents (methane, water, and ammonia) and find that methane and water are the upper and lower bounds, respectively, of conductivity and velocity in these systems. These physical properties provide critical insights that advance the modeling of thermo‐chemical structures and dynamics within icy bodies.

At ambient pressure, bulk SrCoO$_{3}$ is a ferromagnetic (FM) metal in cubic perovskite structure. By contrast, magnetic properties of epitaxial SrCoO$_{3}$ thin films, especially at high tensile strain ($\varepsilon \gtrsim 3$\%), remain unclear: Previous calculations had predicted antiferromagnetic (AFM) states more energetically favorable in this regime, but recent experiments indicated a FM insulating state. In this work, using first-principles calculations, we perform an extensive search for the structural, spin, magnetic, and orbital states of SrCoO$_{3}$ thin films. Our calculations indicate that at $0 < \varepsilon \lesssim 2.5$\%, SrCoO$_{3}$ favors a FM half-metallic state with intermediate-spin ($t_{2g}^{5}e_{g}^{1}$-like) Co exhibiting $d^{6}\underline L$ character. At $\varepsilon \gtrsim 2.5$\%, a FM insulating state with high-spin ($t_{2g}^{4}e_{g}^{2}$-like) Co dominates. This FM insulating state is achieved via complicated orbital ordering, cooperative Jahn--Teller distortion, and octahedral tilting about all three crystal axes.

Ferromagnesite $[({\mathrm{Mg}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}){\mathrm{CO}}_{3}]$, also referred to as magnesiosiderite at high iron concentration ($xg0.5$), is a solid solution of magnesite $(\mathrm{Mg}{\mathrm{CO}}_{3}$) and siderite ($\mathrm{Fe}{\mathrm{CO}}_{3}$). Ferromagnesite is believed to enter the Earth's lower mantle via subduction and is considered a major carbon carrier in the Earth's lower mantle, playing a key role in the Earth's deep carbon cycle. Experiments have shown that ferromagnesite undergoes a pressure-induced spin crossover, accompanied by volume and elastic anomalies, in the lower-mantle pressure range. In this work, we investigate thermal properties of $({\mathrm{Mg}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}){\mathrm{CO}}_{3}$ ($0lx\ensuremath{\le}1$) using first-principles calculations. We show that nearly all thermal properties of ferromagnesite are drastically altered by iron spin crossover, including anomalous reduction of volume, anomalous softening of bulk modulus, and anomalous increases of thermal expansion, heat capacity, and the Gr\"uneisen parameter. Remarkably, the anomaly of heat capacity remains prominent (up to $\ensuremath{\sim}40%$) at high temperature without smearing out, which suggests that iron spin crossover may significantly affect the thermal properties of subducting slabs and the Earth's deep carbon cycle.

This repository contains experimental data on the thermal conductivity and compressional velocity of methane (CH4) up to 45 GPa at room temperature and theoretical calculations of methane's equation of state, heat capacity, and bulk sound velocity from 5-100 GPa and 0-1200 K. These datasets are presented in a manuscript submitted to Journal of Geophysical Research: Planets by Meyer, D.W.; Hsieh, W.P.; Hsu, H.; Kuo, C.Y.; and Lin, J.F. in Oct. 2021 entitled: Thermal conductivity and compressional velocity of methane at high pressure: Insights into thermal transport properties of icy planetary interiors.

Fe-bearing MgO [(Mg$_{1-x}$Fe$_x$)O] is considered a major constituent of terrestrial exoplanets. Crystallizing in the B1 structure in the Earth's lower mantle, (Mg$_{1-x}$Fe$_x$)O undergoes a high-spin (HS, $S=2$) to low-spin (LS, $S=0$) transition at $\sim$45 GPa, accompanied by anomalous changes of this mineral's physical properties, while the intermediate-spin (IS, $S=1$) state has not been observed. In this work, we investigate (Mg$_{1-x}$Fe$_x$)O ($x \leq 0.25$) up to $1.8$ TPa via first-principles calculations. Our calculations indicate that (Mg$_{1-x}$Fe$_x$)O undergoes a simultaneous structural and spin transition at $\sim$0.6 TPa, from the B1 phase LS state to the B2 phase IS state, with Fe's total electron spin ($S$) re-emerging from $0$ to $1$ at ultrahigh pressure. Upon further compression, an IS--LS transition occurs in the B2 phase. Depending on the Fe concentration ($x$), metal--insulator transition and rhombohedral distortions can also occur in the B2 phase. These results suggest that Fe and spin transition may affect planetary interiors over a vast pressure range.

Magnetic properties of fully oxygenated bare CuO nanoparticles have been investigated using magnetization, X-ray diffraction, neutron diffraction, and Raman scattering measurements. The Langevin field profile is clearly revealed in the isothermal magnetization of 8.8 nm CuO nanoparticle assembly even at 300 K, revealing a 172 times enhancement of the ferromagnetic responses over that of bulk CuO. Surface magnetization of 8.8 nm CuO reaches 18% of the core magnetization. The Cu spins in 8.8 nm CuO order below 400 K, which is 1.7 times higher than the 231 K observed in bulk CuO. A relatively simple magnetic structure that may be indexed using a modulation vector of (0.2, 0, 0.2) was found for the 8.8 nm CuO, but no magnetic incommensurability was observed in bulk CuO. The Cu spins in 8.8 nm CuO form spin density waves with length scales of 5 chemical unit cells long along the crystallographic a- and c-axis directions. Considerable amounts of electronic charge shift from around the Cu lattice sites toward the interconnecting regions of two neighboring Cu-Cu ions, resulting in a stronger ferromagnetic direct exchange interaction for the neighboring Cu spins in 8.8 nm CuO.

Weyl semimetals are novel topological conductors that host Weyl fermions as emergent quasiparticles. In this Rapid Communication, we propose a new type of Weyl semimetal state that breaks both time-reversal symmetry and inversion symmetry in the R AlGe (R= rare− earth) family. Compared to previous predictions of magnetic Weyl semimetal candidates, the prediction of Weyl nodes in R AlGe is more robust and less dependent on the details of the magnetism because the Weyl nodes are generated already by the inversion breaking and the ferromagnetism acts as a simple Zeeman coupling that shifts the Weyl nodes in k space. Moreover, R AlGe offers remarkable tunability, which covers all varieties of Weyl semimetals including type I, type II, inversion breaking, and time-reversal breaking, depending on a suitable choice of the rare-earth elements. Furthermore, the unique noncentrosymmetric and …

Weyl semimetals are novel topological conductors that host Weyl fermions as emergent quasiparticles. In this Rapid Communication, we propose a new type ofWeyl semimetal state that breaks both time-reversal symmetry and inversion symmetry in the RAlGe (R = rare-earth) family. Compared to previous predictions of magnetic Weyl semimetal candidates, the prediction of Weyl nodes in RAlGe is more robust and less dependent on the details of the magnetism because the Weyl nodes are generated already by the inversion breaking and the ferromagnetism acts as a simple Zeeman coupling that shifts theWeyl nodes in k space. Moreover, RAlGe offers remarkable tunability, which covers all varieties ofWeyl semimetals including type I, type II, inversion breaking, and time-reversal breaking, depending on a suitable choice of the rare-earth elements. Furthermore, the unique noncentrosymmetric and ferromagnetic Weyl semimetal state in RAlGe enables the generation of spin currents.

In experiments, strontium cobaltite (SrCoO3) has been confirmed to be a ferromagnetic metal (Curie temperature T-c approximate to 305 K) at ambient conditions and remains in cubic perovskite structure up to similar to 60 GPa. Using local density approximation + self -consistent Hubbard U (LDA+U-sc ) calculations, we show that ferromagnetic metallic SrCoO3 at low pressure is in an intermediate-spin (IS) state with d(6)(L) under bar character: nearly trivalent (Co3+) instead of tetravalent cobalt (Co4+) accompanied by spin-down O-2p electron holes (ligand holes (L) under bar). Our calculations further predict that upon compression ( greater than or similar to 7 GPa), SrCoO3 undergoes a transition to a low-spin (LS) ferromagnetic half-metal with an energy gap opened in the spin-up channel. Compared to the metallic IS state, the half-metallic LS state exhibits even more prominent d(6)(L) under bar character, including nearly nonmagnetic Co3+ and exceptionally large oxygen magnetic moments, which contribute most of the magnetization. By analyzing x-ray diffraction data of compressed single-crystal SrCoO3, we point out an anomalous volume reduction of similar to 1%. This previously unnoticed volume anomaly is in great agreement with our predictive calculations, providing quantitative evidence for the simultaneous metal-half-metal and spin transition in SrCoO3.