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Tetsuya Komabayashi - One of the best experts on this subject based on the ideXlab platform.
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carbon depleted Outer Core revealed by sound velocity measurements of liquid iron carbon alloy
Nature Communications, 2015Co-Authors: Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Haruka Ozawa, Shigehiko Tateno, Kei HiroseAbstract:The relative abundance of light elements in the Earth’s Core has long been controversial. Recently, the presence of carbon in the Core has been emphasized, because the density and sound velocities of the inner Core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the Outer Core, about 4% faster than that of liquid iron, is consistent with the presence of 4–5 at.% carbon. However, that amount of carbon is too small to account for the Outer Core density deficit, suggesting that carbon cannot be a predominant light element in the Core. The composition of the Earth's Core, particularly the light elements present, is not well constrained. Here, the authors report sound velocities of liquid iron-carbon alloy as measured at very high pressures using inelastic X-ray scattering and suggest that carbon cannot be predominant in the Outer Core.
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carbon depleted Outer Core revealed by sound velocity measurements of liquid iron carbon alloy
Nature Communications, 2015Co-Authors: Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Haruka Ozawa, Shigehiko Tateno, Kei HiroseAbstract:The relative abundance of light elements in the Earth's Core has long been controversial. Recently, the presence of carbon in the Core has been emphasized, because the density and sound velocities of the inner Core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the Outer Core, about 4% faster than that of liquid iron, is consistent with the presence of 4-5 at.% carbon. However, that amount of carbon is too small to account for the Outer Core density deficit, suggesting that carbon cannot be a predominant light element in the Core.
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liquid iron sulfur alloys at Outer Core conditions by first principles calculations
Geophysical Research Letters, 2014Co-Authors: Koichiro Umemoto, Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Kei Hirose, Satoshi Tsutsui, Alfred Q R BaronAbstract:We examined the density, bulk sound (compressional) velocity, and Gruneisen parameter of liquid pure Fe, Fe100H28 (0.50 wt % H), Fe88H40 (0.81 wt % H), and Fe76H52 (1.22 wt % H) at Earth's Outer Core pressure and temperature (P-T) conditions (~100 to 350 GPa, 4000 to 7000 K) based on first-principles molecular dynamics calculations. The results demonstrate that the thermodynamic Gruneisen parameter of liquid iron alloy decreases with increasing pressure, temperature, and hydrogen concentration, indicating a relatively small temperature gradient in the Outer Core when hydrogen is present. Along such temperature profile, both the density and compressional velocity of liquid iron containing ~1 wt % hydrogen match seismological observations. It suggests that hydrogen could be a primary light element in the Core, although the shear velocity of the inner Core is not reconciled with solid Fe-H alloy and thus requires another impurity element.
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thermodynamics of melting relations in the system fe feo at high pressure implications for oxygen in the earth s Core
Journal of Geophysical Research, 2014Co-Authors: Tetsuya KomabayashiAbstract:The thermodynamics of melting relations in the system Fe-FeO was investigated to the Outer Core–inner Core boundary condition from a self-consistent thermodynamic database which was evaluated from the latest static high-pressure (P) and high-temperature (T) experiments. The evaluated database together with an existing nonideal mixing model for liquids reproduces experimental data on the eutectic composition and temperature to P = 50 GPa. On the other hand at the Outer Core pressures (136 to 330 GPa), employing an ideal solution model gives calculated eutectic temperatures of T = 2990–4330 K, which are also consistent with experimental data. Hence, the ideal solution model is applied to calculate the liquid property under Outer Core conditions and yields the eutectic compositions of Fe–7.2–9.1 wt % O. From the Gibbs free energy for the Fe-FeO liquids, I calculated the density, sound velocity, and isentropic temperature gradient of a hypothetical oxygen-bearing Outer Core. Under the Outer Core conditions, the addition of oxygen reduces the compressional wave velocity of iron liquid, moving it away from seismologically constrained values. An overall O-rich bulk Outer Core model is thus excluded. Seismological observations however suggest the presence of a low-velocity layer with a thickness of 60–70 km at the top of the Outer Core. The origin of such a low-velocity layer can be explained by an enrichment of oxygen which might be a consequence of chemical interactions between the Core and mantle.
Shigehiko Tateno - One of the best experts on this subject based on the ideXlab platform.
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carbon depleted Outer Core revealed by sound velocity measurements of liquid iron carbon alloy
Nature Communications, 2015Co-Authors: Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Haruka Ozawa, Shigehiko Tateno, Kei HiroseAbstract:The relative abundance of light elements in the Earth’s Core has long been controversial. Recently, the presence of carbon in the Core has been emphasized, because the density and sound velocities of the inner Core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the Outer Core, about 4% faster than that of liquid iron, is consistent with the presence of 4–5 at.% carbon. However, that amount of carbon is too small to account for the Outer Core density deficit, suggesting that carbon cannot be a predominant light element in the Core. The composition of the Earth's Core, particularly the light elements present, is not well constrained. Here, the authors report sound velocities of liquid iron-carbon alloy as measured at very high pressures using inelastic X-ray scattering and suggest that carbon cannot be predominant in the Outer Core.
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carbon depleted Outer Core revealed by sound velocity measurements of liquid iron carbon alloy
Nature Communications, 2015Co-Authors: Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Haruka Ozawa, Shigehiko Tateno, Kei HiroseAbstract:The relative abundance of light elements in the Earth's Core has long been controversial. Recently, the presence of carbon in the Core has been emphasized, because the density and sound velocities of the inner Core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the Outer Core, about 4% faster than that of liquid iron, is consistent with the presence of 4-5 at.% carbon. However, that amount of carbon is too small to account for the Outer Core density deficit, suggesting that carbon cannot be a predominant light element in the Core.
Kei Hirose - One of the best experts on this subject based on the ideXlab platform.
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carbon depleted Outer Core revealed by sound velocity measurements of liquid iron carbon alloy
Nature Communications, 2015Co-Authors: Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Haruka Ozawa, Shigehiko Tateno, Kei HiroseAbstract:The relative abundance of light elements in the Earth’s Core has long been controversial. Recently, the presence of carbon in the Core has been emphasized, because the density and sound velocities of the inner Core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the Outer Core, about 4% faster than that of liquid iron, is consistent with the presence of 4–5 at.% carbon. However, that amount of carbon is too small to account for the Outer Core density deficit, suggesting that carbon cannot be a predominant light element in the Core. The composition of the Earth's Core, particularly the light elements present, is not well constrained. Here, the authors report sound velocities of liquid iron-carbon alloy as measured at very high pressures using inelastic X-ray scattering and suggest that carbon cannot be predominant in the Outer Core.
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carbon depleted Outer Core revealed by sound velocity measurements of liquid iron carbon alloy
Nature Communications, 2015Co-Authors: Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Haruka Ozawa, Shigehiko Tateno, Kei HiroseAbstract:The relative abundance of light elements in the Earth's Core has long been controversial. Recently, the presence of carbon in the Core has been emphasized, because the density and sound velocities of the inner Core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the Outer Core, about 4% faster than that of liquid iron, is consistent with the presence of 4-5 at.% carbon. However, that amount of carbon is too small to account for the Outer Core density deficit, suggesting that carbon cannot be a predominant light element in the Core.
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liquid iron sulfur alloys at Outer Core conditions by first principles calculations
Geophysical Research Letters, 2014Co-Authors: Koichiro Umemoto, Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Kei Hirose, Satoshi Tsutsui, Alfred Q R BaronAbstract:We examined the density, bulk sound (compressional) velocity, and Gruneisen parameter of liquid pure Fe, Fe100H28 (0.50 wt % H), Fe88H40 (0.81 wt % H), and Fe76H52 (1.22 wt % H) at Earth's Outer Core pressure and temperature (P-T) conditions (~100 to 350 GPa, 4000 to 7000 K) based on first-principles molecular dynamics calculations. The results demonstrate that the thermodynamic Gruneisen parameter of liquid iron alloy decreases with increasing pressure, temperature, and hydrogen concentration, indicating a relatively small temperature gradient in the Outer Core when hydrogen is present. Along such temperature profile, both the density and compressional velocity of liquid iron containing ~1 wt % hydrogen match seismological observations. It suggests that hydrogen could be a primary light element in the Core, although the shear velocity of the inner Core is not reconciled with solid Fe-H alloy and thus requires another impurity element.
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Low Core-mantle boundary temperature inferred from the solidus of pyrolite
Science, 2014Co-Authors: Ryuichi Nomura, Yasuo Ohishi, Akira Tsuchiyama, Akira Miyake, Kei Hirose, Kentaro Uesugi, Yuichiro UenoAbstract:The melting temperature of Earth’s mantle provides key constraints on the thermal structures of both the mantle and the Core. Through high-pressure experiments and three-dimensional x-ray microtomographic imaging, we showed that the solidus temperature of a primitive (pyrolitic) mantle is as low as 3570 ± 200 kelvin at pressures expected near the boundary between the mantle and the Outer Core. Because the lowermost mantle is not globally molten, this provides an upper bound of the temperature at the Core-mantle boundary (TCMB). Such remarkably low TCMB implies that the post-perovskite phase is present in wide areas of the lowermost mantle. The low TCMB also requires that the melting temperature of the Outer Core is depressed largely by impurities such as hydrogen.
Yoichi Nakajima - One of the best experts on this subject based on the ideXlab platform.
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structure and density of fe c liquid alloys under high pressure
Journal of Geophysical Research, 2017Co-Authors: Guillaume Morard, Yoichi Nakajima, Denis Andrault, Daniele Antonangeli, Anneline Auzende, E Boulard, S Cervera, A N Clark, Oliver T LordAbstract:The density and structure of liquid Fe-C alloys have been measured up to 58 GPa and 3,200 K by in situ X-ray diffraction using a Paris-Edinburgh press and laser-heated diamond anvil cell. Study of the pressure evolution of the local structure inferred by X-ray diffraction measurements is important to understand the compression mechanism of the liquid. Obtained data show that the degree of compression is greater for the first coordination sphere than the second and third coordination spheres. The extrapolation of the measured density suggests that carbon cannot be the only light element alloyed to iron in the Earth's Core, as 8–16 at % C (1.8–3.7 wt % C) would be necessary to explain the density deficit of the Outer Core relative to pure Fe. This concentration is too high to account for Outer Core velocity. The presence of other light elements (e.g., O, Si, S, and H) is thus required.
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carbon depleted Outer Core revealed by sound velocity measurements of liquid iron carbon alloy
Nature Communications, 2015Co-Authors: Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Haruka Ozawa, Shigehiko Tateno, Kei HiroseAbstract:The relative abundance of light elements in the Earth’s Core has long been controversial. Recently, the presence of carbon in the Core has been emphasized, because the density and sound velocities of the inner Core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the Outer Core, about 4% faster than that of liquid iron, is consistent with the presence of 4–5 at.% carbon. However, that amount of carbon is too small to account for the Outer Core density deficit, suggesting that carbon cannot be a predominant light element in the Core. The composition of the Earth's Core, particularly the light elements present, is not well constrained. Here, the authors report sound velocities of liquid iron-carbon alloy as measured at very high pressures using inelastic X-ray scattering and suggest that carbon cannot be predominant in the Outer Core.
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carbon depleted Outer Core revealed by sound velocity measurements of liquid iron carbon alloy
Nature Communications, 2015Co-Authors: Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Haruka Ozawa, Shigehiko Tateno, Kei HiroseAbstract:The relative abundance of light elements in the Earth's Core has long been controversial. Recently, the presence of carbon in the Core has been emphasized, because the density and sound velocities of the inner Core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the Outer Core, about 4% faster than that of liquid iron, is consistent with the presence of 4-5 at.% carbon. However, that amount of carbon is too small to account for the Outer Core density deficit, suggesting that carbon cannot be a predominant light element in the Core.
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liquid iron sulfur alloys at Outer Core conditions by first principles calculations
Geophysical Research Letters, 2014Co-Authors: Koichiro Umemoto, Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Kei Hirose, Satoshi Tsutsui, Alfred Q R BaronAbstract:We examined the density, bulk sound (compressional) velocity, and Gruneisen parameter of liquid pure Fe, Fe100H28 (0.50 wt % H), Fe88H40 (0.81 wt % H), and Fe76H52 (1.22 wt % H) at Earth's Outer Core pressure and temperature (P-T) conditions (~100 to 350 GPa, 4000 to 7000 K) based on first-principles molecular dynamics calculations. The results demonstrate that the thermodynamic Gruneisen parameter of liquid iron alloy decreases with increasing pressure, temperature, and hydrogen concentration, indicating a relatively small temperature gradient in the Outer Core when hydrogen is present. Along such temperature profile, both the density and compressional velocity of liquid iron containing ~1 wt % hydrogen match seismological observations. It suggests that hydrogen could be a primary light element in the Core, although the shear velocity of the inner Core is not reconciled with solid Fe-H alloy and thus requires another impurity element.
Haruka Ozawa - One of the best experts on this subject based on the ideXlab platform.
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carbon depleted Outer Core revealed by sound velocity measurements of liquid iron carbon alloy
Nature Communications, 2015Co-Authors: Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Haruka Ozawa, Shigehiko Tateno, Kei HiroseAbstract:The relative abundance of light elements in the Earth’s Core has long been controversial. Recently, the presence of carbon in the Core has been emphasized, because the density and sound velocities of the inner Core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the Outer Core, about 4% faster than that of liquid iron, is consistent with the presence of 4–5 at.% carbon. However, that amount of carbon is too small to account for the Outer Core density deficit, suggesting that carbon cannot be a predominant light element in the Core. The composition of the Earth's Core, particularly the light elements present, is not well constrained. Here, the authors report sound velocities of liquid iron-carbon alloy as measured at very high pressures using inelastic X-ray scattering and suggest that carbon cannot be predominant in the Outer Core.
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carbon depleted Outer Core revealed by sound velocity measurements of liquid iron carbon alloy
Nature Communications, 2015Co-Authors: Yoichi Nakajima, Saori Imada, Tetsuya Komabayashi, Haruka Ozawa, Shigehiko Tateno, Kei HiroseAbstract:The relative abundance of light elements in the Earth's Core has long been controversial. Recently, the presence of carbon in the Core has been emphasized, because the density and sound velocities of the inner Core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the Outer Core, about 4% faster than that of liquid iron, is consistent with the presence of 4-5 at.% carbon. However, that amount of carbon is too small to account for the Outer Core density deficit, suggesting that carbon cannot be a predominant light element in the Core.
