2024/12/02 更新

写真a

イクタ ダイジョウ
生田 大穣
Daijo IKUTA
所属
惑星物質研究所 一般スーパーテクニシャン
職名
一般スーパーテクニシャン
外部リンク

学位

  • 博士(人間・環境学) ( 2008年3月   京都大学 )

研究キーワード

  • 放射光

  • 固体地球科学

  • 高圧物理学

  • 地球物理学

  • 結晶学

  • 鉱物学

研究分野

  • 自然科学一般 / 固体地球科学

学歴

  • 京都大学   Graduate School of Human and Environmental Studies (Department of Interdisciplinary Environment)   Doctor Course

    2005年4月 - 2008年3月

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    国名: 日本国

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  • 京都大学   Graduate School of Human and Environmental Studies (Department of Interdisciplinary Environment)   Master Course

    2003年4月 - 2005年3月

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    国名: 日本国

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経歴

  • 岡山大学   惑星物質研究所

    2022年12月 - 現在

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  • 東北大学   理学研究科 地学専攻

    2016年9月 - 2022年11月

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    国名:日本国

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  • カーネギー地球物理学研究所   HPCAT部門

    2007年7月 - 2016年8月

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    国名:アメリカ合衆国

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所属学協会

  • 日本高圧力学会

    2018年 - 現在

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  • 日本地球惑星科学連合

    2015年 - 現在

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論文

  • Density deficit of Earth's core revealed by a multimegabar primary pressure scale 査読 国際共著 国際誌

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakamaki, R. Heid, D. Ishikawa, A. Q. R. Baron

    Science Advances   9 ( 36 )   eadh8706   2023年9月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Association for the Advancement of Science  

    An accurate pressure scale is a fundamental requirement to understand planetary interiors. Here, we establish a primary pressure scale extending to the multimegabar pressures of Earth's core, by combined measurement of the acoustic velocities and the density from a rhenium sample in a diamond anvil cell using inelastic x-ray scattering and x-ray diffraction. Our scale agrees well with previous primary scales and shock Hugoniots in each experimental pressure range and reveals that previous scales have overestimated laboratory pressures by at least 20% at 230 gigapascals. It suggests that the light element content in Earth's inner core (the density deficit relative to iron) is likely to be double what was previously estimated, or Earth's inner core temperature is much higher than expected, or some combination thereof.

    DOI: 10.1126/sciadv.adh8706

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  • Sound velocity of hexagonal close-packed iron to the Earth's inner core pressure 査読 国際誌

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakai, D. Ishikawa, A. Q. R. Baron

    Nature Communications   13   7211   2022年11月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer  

    Here we determine the compressional and shear wave velocities (vp and vs) of hexagonal close-packed iron, a candidate for the main constituent of the Earth's inner core, to pressures above 300 gigapascals using a newly designed diamond anvil cell and inelastic x-ray scattering combined with x-ray diffraction. The present results reveal that the vp and vs of the Preliminary reference Earth model (PREM) inner core are 4(±2)% and 36(±17)% slower than those of the pure iron, respectively at the centre of the core. The density and sound velocity of the PREM inner core can be explained by addition of 3(±1) wt% silicon and 3(±2) wt% sulphur to iron-5 wt% nickel alloy. Our suggested inner core composition is consistent with the existing outer core model with oxygen, as the growth of the inner core may have created a secular enrichment of the element in the outer core.

    DOI: 10.1038/s41467-022-34789-2

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  • Two-phase mixture of iron-nickel-silicon alloys in the Earth's inner core 査読 国際誌

    D. Ikuta, E. Ohtani, N. Hirao

    Communications Earth & Environment   2   225   2021年10月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer  

    The Earth's inner core comprises iron-nickel alloys with light elements. However, there is no clarity on the phase properties of these alloys. Here we show phase relations and equations of state of iron-nickel and iron-nickel-silicon alloys up to 186 gigapascals and 3090 kelvin. An ordered derivative of the body-centred cubic structure (B2) phase was observed in these alloys. Results show that nickel and silicon influence the stability field associated with the two-phase mixture of B2 and hexagonal close-packed phases under core conditions. The two-phase mixture can give the inner core density of the preliminary reference Earth model. The compressional wave velocity of the two-phase mixture under inner core conditions is consistent with that of the preliminary reference Earth model. Therefore, a mixture of B2 and hexagonal close-packed phases may exist in the inner core and accounts for the seismological properties of the inner core such as density and velocity deficits.

    DOI: 10.1038/s43247-021-00298-1

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  • Interstitial hydrogen atoms in face-centered cubic iron in the Earth's core 査読 国際誌

    D. Ikuta, E. Ohtani, A. Sano-Furukawa, Y. Shibazaki, H. Terasaki, L. Yuan, T. Hattori

    Scientific Reports   9   7108   2019年5月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer  

    Hydrogen is likely one of the light elements in the Earth's core. Despite its importance, no direct observation has been made of hydrogen in an iron lattice at high pressure. We made the first direct determination of site occupancy and volume of interstitial hydrogen in a face-centered cubic (fcc) iron lattice up to 12 GPa and 1200 K using the in situ neutron diffraction method. The transition temperatures from the body-centered cubic and the double-hexagonal close-packed phases to the fcc phase were higher than reported previously. At pressures <5 GPa, the hydrogen content in the fcc iron hydride lattice (x) was small at x < 0.3, but increased to x > 0.8 with increasing pressure. Hydrogen atoms occupy both octahedral (O) and tetrahedral (T) sites; typically 0.870(±0.047) in O-sites and 0.057(±0.035) in T-sites at 12 GPa and 1200 K. The fcc lattice expanded approximately linearly at a rate of 2.22(±0.36) A3 per hydrogen atom, which is higher than previously estimated (1.9 A3/H). The lattice expansion by hydrogen dissolution was negligibly dependent on pressure. The large lattice expansion by interstitial hydrogen reduced the estimated hydrogen content in the Earth's core that accounted for the density deficit of the core. The revised analyses indicate that whole core may contain hydrogen of 80(±31) times of the ocean mass with 79(±30) and 0.8(±0.3) ocean mass for the outer and inner cores, respectively.

    DOI: 10.1038/s41598-019-43601-z

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  • Viscosity anomaly of a metallic glass-forming liquid under high pressure 査読 国際共著 国際誌

    Q. Wang, H. Lou, Y. Kono, D. Ikuta, Z. Zeng, Q. Zeng

    Journal of Non-Crystalline Solids   615   122412   2023年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier  

    Viscosity, as a critical property closely associated with the glass-forming ability of a liquid, has been extensively studied with varying temperatures. However, its pressure dependence has not been well explored yet due to experimental difficulties. Here, we measured the viscosity of a metallic glass-forming liquid, Zr46Cu37.6Ag8.4Al8, at pressures up to 6.1 GPa above the melting points by falling-sphere viscometry with ultrafast synchrotron x-ray imaging. Overall, the viscosity increases with pressure, while surprisingly, there is an abrupt drop between 3.2 GPa and 3.7 GPa, indicating the possible existence of a pressure-induced liquid-to-liquid transition. Pressure could change the short- and medium-range orders in the multicomponent glass-forming liquid, as suggested by the different crystalline outcomes after cooling to room temperature at high- and low-pressure ranges. Our work extended the viscosity investigation of metallic glass-forming liquids to the high-pressure regime, which will expand our understanding of liquid-liquid transitions and metallic glass formation.

    DOI: 10.1016/j.jnoncrysol.2023.122412

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  • Sound velocity measurements of B2-Fe-Ni-Si alloy under high pressure by inelastic x-ray scattering: Implications for the composition of Earth's core 査読 国際共著 国際誌

    S. Dominijanni, C. A. McCammon, E. Ohtani, D. Ikuta, T. Sakamaki, T. Ishii, G. Criniti, L. S. Dubrovinsky, S. Khandarkhaeva, T. Fedotenko, K. Glazyrin, H. Uchiyama, H. Fukui, A. Q. R. Baron

    Geophysical Research Letters   49 ( 15 )   e2021GL096405   2022年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union  

    Elastic properties of B2-Fe0.67Ni0.06Si0.27 (15 wt.% Si) alloy have been investigated by combined high-resolution inelastic x-ray scattering and powder x-ray diffraction in diamond anvil cells up to 100 GPa at room temperature. Densities (ρ), compressional (VP) and shear (VS) wave velocities were extrapolated to inner core conditions to enable comparison with the preliminary reference Earth model. The modeled aggregate compressional and shear wave velocities and densities of the two-phase mixture of B2-Fe0.67Ni0.06Si0.27 and hcp-Fe-Ni are consistent with inner core PREM values of VP, VS, and ρ based on a linear mixing model with 30(5) vol % B2-Fe0.67Ni0.06Si0.27 and 70(5) vol % hcp Fe-Ni, which corresponds to ~3-5 wt.% Si and ~5-12 wt.% Ni.

    DOI: 10.1029/2021gl096405

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  • Thermal equation of state of Fe3C to 327 GPa and carbon in the core 査読 国際誌

    S. Takahashi, E. Ohtani, D. Ikuta, S. Kamada, T. Sakamaki, N. Hirao, Y. Ohishi

    Minerals   9 ( 12 )   744   2019年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI  

    The density and sound velocity structure of the Earth's interior is modeled on seismological observations and is known as the preliminary reference Earth model (PREM). The density of the core is lower than that of pure Fe, which suggests that the Earth's core contains light elements. Carbon is one plausible light element that may exist in the core. We determined the equation of state (EOS) of Fe3C based on in situ high-pressure and high-temperature x-ray diffraction experiments using a diamond anvil cell. We obtained the P-V data of Fe3C up to 327 GPa at 300 K and 70-180 GPa up to around 2300 K. The EOS of nonmagnetic (NM) Fe3C was expressed by two models using two different pressure scales and the third-order Birch-Murnaghan EOS at 300 K with the Mie-Gruneisen-Debye EOS under high-temperature conditions. The EOS can be expressed with parameters of V0 = 148.8(±1.0) A3, K0 = 311.1(±17.1) GPa, K0' = 3.40(±0.1), γ0 = 1.06(±0.42), and q = 1.92(±1.73), with a fixed value of θ0 = 314 K using the KBr pressure scale (Model 1), and V0 = 147.3(±1.0) A3, K0 = 323.0(±16.6) GPa, K0' = 3.43(±0.09), γ0 = 1.37(±0.33), and q = 0.98(±1.01), with a fixed value of θ0 = 314 K using the MgO pressure scale (Model 2). The density of Fe3C under inner core conditions (assuming P = 329 GPa and T = 5000 K) calculated from the EOS is compatible with the PREM inner core.

    DOI: 10.3390/min9120744

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  • Pressure-enhanced interplay between lattice, spin, and charge in the mixed perovskite La2FeMnO6 査読 国際共著 国際誌

    N. Li, F. Fan, F. Sun, Y. Wang, Y. Zhao, F. Liu, Q. Zhang, D. Ikuta, Y. Xiao, P. Chow, S. M. Heald, C. Sun, D. Brewe, A. Li, X. Lu, H. K. Mao, D. I. Khomskii, H. Wu, W. Yang

    Physical Review B   99 ( 19 )   195115   2019年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Physical Society  

    Spin crossover plays a central role in the structural instability, net magnetic moment modification, metallization, and even in superconductivity in corresponding materials. Most reports on the pressure-induced spin crossover with a large volume collapse have so far focused on compounds with a single transition metal. Here we report a comprehensive high-pressure investigation of a mixed Fe-Mn perovskite La2FeMnO6. Under pressure, the strong coupling between Fe and Mn leads to a combined valence/spin transition: Fe3+(S=5/2)→Fe2+(S=0) and Mn3+(S=2)→Mn4+(S=3/2), with an isostructural phase transition. The spin transitions of both Fe and Mn are offset by ~20 GPa of the onset pressure, and the lattice collapse occurs in between. Interestingly, Fe3+ ion shows an abnormal behavior when it reaches a lower valence state (Fe2+) accompanied by a +0.5 eV energy shift in the Fe K-absorption edge at 15 GPa. This process is associated with the charge-spin-orbital state transition from high spin Fe3+ to low spin Fe2+, caused by the significantly enhanced t2g-eg crystal field splitting in the compressed lattice under high pressure. Density functional theory calculations confirm the energy preference of the high-pressure state with charge redistribution accompanied by spin state transition of Fe ions. Moreover, La2FeMnO6 maintains semiconductor behaviors even when the pressure reached 144.5 GPa as evidenced by the electrical transport measurements, despite the huge resistivity decreasing seven orders of magnitude compared with that at ambient pressure. The investigation carried out here demonstrates high flexibility of double perovskites and their good potentials for optimizing the functionality of these materials.

    DOI: 10.1103/physrevb.99.195115

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  • Chemical reactions between Fe and H2O up to megabar pressures and implications for water storage in the Earth's mantle and core 査読 国際共著 国際誌

    L. Yuan, E. Ohtani, D. Ikuta, S. Kamada, J. Tsuchiya, H. Naohisa, Y. Ohishi, A. Suzuki

    Geophysical Research Letters   45 ( 3 )   1330 - 1338   2018年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union  

    We investigated the phase relations of the Fe-H2O system at high pressures based on in situ x-ray diffraction experiments and first-principles calculations and demonstrate that FeHx and FeO are present at pressures less than ~78 GPa. A recently reported pyrite-structured FeO2 was identified in the Fe-H2O system at pressures greater than ~78 GPa after laser heating. The phase observed in this study has a unit cell volume 8%-11% larger than that of FeO2, produced in the Fe-O binary system reported previously, suggesting that hydrogen might be retained in a FeO2Hx crystal structure. Our observations indicate that H2O is likely introduced into the deep Earth through reaction between iron and water during the accretion and separation of the metallic core. Additionally, reaction between Fe and H2O would occur at the core-mantle boundary, given water released from hydrous subducting slabs that intersect with the metallic core. Accumulation of volatile-bearing iron compounds may provide new insights into the enigmatic seismic structures observed at the base of the lower mantle.

    DOI: 10.1002/2017gl075720

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  • Structural analysis of liquid aluminum at high pressure and high temperature using the hard sphere model 査読 国際共著 国際誌

    D. Ikuta, Y. Kono, G. Shen

    Journal of Applied Physics   120 ( 13 )   135901   2016年10月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Institute of Physics  

    The structure of liquid aluminum is measured up to 6.9 GPa and 1773 K using a multi-angle energy-dispersive x-ray diffraction method in a Paris-Edinburgh press. The effect of pressure and temperature on the structure and density of liquid aluminum is analyzed by means of the hard sphere model. Peak positions in the structure factor of liquid aluminum show a nearly constant value with varying temperatures at ~1-2 GPa and slightly change with varying pressures up to 6.9 GPa at 1173-1773 K. In contrast, the height of the first peak in the structure factor significantly changes with varying pressures and temperatures. Hard sphere model analysis shows that the structure of liquid aluminum in the pressure-temperature range of this study is controlled mostly by the packing fraction with only a minor change in hard sphere diameters. The obtained packing fractions and hard sphere diameters are used to calculate densities of liquid aluminum at high pressure-temperature conditions.

    DOI: 10.1063/1.4963278

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  • Pressure and temperature dependence of the structure of liquid Sn up to 5.3 GPa and 1373 K 査読 国際共著 国際誌

    D. Ikuta, Y. Kono, G. Shen

    High Pressure Research   36 ( 4 )   533 - 548   2016年5月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Taylor & Francis  

    Pressure and temperature dependence of the structure of liquid Sn has been measured up to 5.3 GPa and 1373 K using multi-angle energy-dispersive x-ray diffraction in Paris-Edinburgh cell. Under nearly isobar condition at ~1 GPa, liquid Sn displays a normal behavior with gradual structural changes with temperature up to 1373 K. Under isothermal compressions at 850 and 1373 K, however, the structure factors of liquid Sn both show a turn-over at ~3 GPa in the height of the first diffraction peak. According to the hard sphere cluster model, the structure of liquid Sn may be viewed as two different types of clusters. Below ~3 GPa, it is shown that the packing fraction of the dominant cluster (occupying ~0.94 fraction) changes with compression, while above ~3 GPa, the packing fractions and the hard sphere diameters of both clusters start to influence the structure, causing significant changes with increasing pressure. Our results suggest that the compression behavior of liquid Sn changes from localized densification only in one cluster below ~3 GPa to homogeneous structural changes in both clusters above ~3 GPa.

    DOI: 10.1080/08957959.2016.1185520

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  • Ultrahigh-pressure polyamorphism in GeO2 glass with coordination number >6 査読 国際共著 国際誌

    Y. Kono, C. Kenney-Benson, D. Ikuta, Y. Shibazaki, Y. Wang, G. Shen

    Proceedings of the National Academy of Sciences   113 ( 13 )   3436 - 3441   2016年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:National Academy of Sciences  

    Knowledge of pressure-induced structural changes in glasses is important in various scientific fields as well as in engineering and industry. However, polyamorphism in glasses under high pressure remains poorly understood because of experimental challenges. Here we report new experimental findings of ultrahigh-pressure polyamorphism in GeO2 glass, investigated using a newly developed double-stage large-volume cell. The Ge-O coordination number (CN) is found to remain constant at ~6 between 22.6 and 37.9 GPa. At higher pressures, CN begins to increase rapidly and reaches 7.4 at 91.7 GPa. This transformation begins when the oxygen-packing fraction in GeO2 glass is close to the maximal dense-packing state (the Kepler conjecture = ~0.74), which provides new insights into structural changes in network-forming glasses and liquids with CN higher than 6 at ultrahigh-pressure conditions.

    DOI: 10.1073/pnas.1524304113

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  • Elastic softening in Fe7C3 with implications for Earth's deep carbon reservoirs 査読 国際共著 国際誌

    J. Liu, J. Li, D. Ikuta

    Journal of Geophysical Research: Solid Earth   121 ( 3 )   1514 - 1524   2016年2月

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    担当区分:最終著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union  

    Iron carbide Fe7C3 has recently emerged as a potential host of reduced carbon in Earth's mantle and a candidate component of the inner core, but the equation of state of Fe7C3 is still uncertain, partly because the nature of pressure-induced magnetic transitions in Fe7C3 and their elastic effects remain controversial. Here we report the compression curve of hexagonal Fe7C3 in neon medium with dense pressure sampling and in comparison with pure iron in the same loading. The results revealed elastic softening between 7 GPa and 20 GPa, which can be attributed to noncollinear alignment of spin moments in a state between the ferromagnetic and paramagnetic phases, as expected for Invar-type alloys. The volume reduction associated with the softening would enhance the stability of Fe7C3 in the deeper part of the upper mantle and transition zone. As a result of subsequent spin crossover at higher pressures, Fe7C3 at inner core conditions likely occurs as the nonmagnetic phase, which remains a candidate for the major component of the Earth's central sphere.

    DOI: 10.1002/2015jb012701

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  • New developments in micro-x-ray diffraction and x-ray absorption spectroscopy for high-pressure research at 16-BM-D at the Advanced Photon Source 査読 国際共著 国際誌

    C. Park, D. Popov, D. Ikuta, C. Lin, C. Kenney-Benson, E. Rod, A. Bommannavar, G. Shen

    Review of Scientific Instruments   86 ( 7 )   072205   2015年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Institute of Physics  

    The monochromator and focusing mirrors of the 16-BM-D beamline, which is dedicated to high-pressure research with micro-X-ray diffraction (micro-XRD) and x-ray absorption near edge structure (XANES) (6-45 keV) spectroscopy, have been recently upgraded. Monochromatic x-rays are selected by a Si (111) double-crystal monochromator operated in an artificial channel-cut mode and focused to 5 μm × 5 μm (FWHM) by table-top Kirkpatrick-Baez type mirrors located near the sample stage. The typical x-ray flux is ~5×10^8 photons/s at 30 keV. The instrumental resolution, Δq/qmax, reaches to 2×10^-3 and is tunable through adjustments of the detector distance and x-ray energy. The setup is stable and reproducible, which allows versatile application to various types of experiments including resistive heating and cryogenic cooling as well as ambient temperature compression. Transmission XANES is readily combined with micro-XRD utilizing the fixed-exit feature of the monochromator, which allows combined XRD-XANES measurements at a given sample condition.

    DOI: 10.1063/1.4926893

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  • High-pressure studies of Bi2S3 査読 国際共著 国際誌

    I. Efthimiopoulos, J. Kemichick, X. Zhou, S. V. Khare, D. Ikuta, Y. Wang

    The Journal of Physical Chemistry A   118 ( 9 )   1713 - 1720   2014年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Chemical Society  

    The high-pressure structural and vibrational properties of Bi2S3 have been probed up to 65 GPa with a combination of experimental and theoretical methods. The ambient-pressure Pnma structure is found to persist up to 50 GPa; further compression leads to structural disorder. Closer inspection of our structural and Raman spectroscopic results reveals notable compressibility changes in specific structural parameters of the Pnma phase beyond 4-6 GPa. By taking the available literature into account, we speculate that a second-order isostructural transition is realized near that pressure, originating probably from a topological modification of the Bi2S3 electronic structure near that pressure. Finally, the Bi3+ lone-electron pair (LEP) stereochemical activity decreases against pressure increase; an utter vanishing, however, is not expected until 1 Mbar. This persistence of the Bi3+ LEP activity in Bi2S3 can explain the absence of any structural transitions toward higher crystalline symmetries in the investigated pressure range.

    DOI: 10.1021/jp4124666

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  • Pressure dependence of the monoclinic phase in (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 solid solutions 査読 国際共著 国際誌

    M. Ahart, S. V. Sinogeikin, O. Shebanova, D. Ikuta, Z. G. Ye, H. K. Mao, R. E. Cohen, R. J. Hemley

    Physical Review B   86 ( 22 )   2012年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Physical Society  

    We combine high-pressure x-ray diffraction, high-pressure Raman scattering, and optical microscopy to investigate a series of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) solid solutions (x=0.2, 0.3, 0.33, 0.35, 0.37, 0.4) in diamond anvil cells up to 20 GPa at 300 K. The Raman spectra show a peak centered at 380 cm-1 starting above 6 GPa for all samples, in agreement with previous observations. X-ray diffraction measurements are consistent with this spectral change indicating a structural phase transition; we find that the triplet at the pseudocubic (220) Bragg peak merges into a doublet above 6 GPa. Our results indicate that the morphotropic phase boundary region (x=0.33-0.37) with the presence of monoclinic symmetry persists up to 7 GPa. The pressure dependence of ferroelectric domains in PMN-0.32PT single crystals was observed using a polarizing optical microscope. The domain wall density decreases with pressure and the domains disappear at a modest pressure of 3 GPa. We propose a pressure-composition phase diagram for PMN-xPT solid solutions.

    DOI: 10.1103/physrevb.86.224111

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  • Direct observation of a pressure-induced precursor lattice in silicon 査読 国際共著 国際誌

    G. Shen, D. Ikuta, S. V. Sinogeikin, Q. Li, Y. Zhang, C. Chen

    Physical Review Letters   109 ( 20 )   205503   2012年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Physical Society  

    Detailed knowledge of atomic-scale structural change is essential for understanding the process and mechanism of phase transitions in solids. We present the direct experimental evidence of a precursor lattice in silicon at high pressures. The precursor lattice may appear to coexist dynamically with the host lattice over a large pressure range through rapid lattice fluctuations. The first-principles calculations are used to elucidate a dynamic lattice-fluctuation mechanism that accounts for the experimental observations. This precursor lattice-fluctuation mechanism for the phase transition goes beyond previously considered reconstructive or displacive processes and provides a novel picture of the underlying dynamics.

    DOI: 10.1103/physrevlett.109.205503

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  • The influence of the Jahn-Teller effect at Fe2+ on the structure of chromite at high pressure 査読 国際共著 国際誌

    A. Kyono, S. A. Gramsch, T. Yamanaka, D. Ikuta, M. Ahart, B. O. Mysen, H. K. Mao, R. J. Hemley

    Physics and Chemistry of Minerals   39 ( 2 )   131 - 141   2011年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer  

    The crystal structure of chromite FeCr2O4 was investigated to 13.7 GPa and ambient temperature with single-crystal x-ray diffraction techniques. The unit-cell parameter decreases continuously from 8.3832(5) to 8.2398(11) A up to 11.8 GPa. A fit to the Birch-Murnaghan equation of state (EoS) based on the P-V data gives: K0 = 209(13) GPa, K' = 4.0 (fixed), and V0 = 588(1) A3. The FeO4 tetrahedra and CrO6 octahedra are compressed isotropically with pressure with their Fe-O and Cr-O bond distances decreasing from 1.996(6) to 1.949(7) A and from 1.997(3) to 1.969(7) A, respectively. The tetrahedral site occupied by the Fe2+ cation is more compressible than the octahedral site occupied by the Cr3+ cation. The resulting EoS parameters for the tetrahedral and the octahedral sites are K0 = 147(9) GPa, K' = 4.0 (fixed), V0 = 4.07(1) A3 and K0 = 275(24) GPa, K' = 4.0 (fixed), V0 = 10.42(2) A3, respectively. A discontinuous volume change is observed between 11.8 and 12.6 GPa. This change indicates a phase transition from a cubic (space group Fd-3m) to a tetragonal structure (space group I41/amd). At the phase transition boundary, the two Cr-O bonds parallel to the c-axis shorten from 1.969(7) to 1.922(17) A and the other four Cr-O bonds parallel to the ab plane elongate from 1.969(7) to 1.987(9) A. This anisotropic deformation of the octahedra leads to tetragonal compression of the unit cell along the c-axis. The angular distortion in the octahedron decreases continuously up to 13.7 GPa, whereas the distortion in the tetrahedron rises dramatically after the phase transition. At the pressure of the phase transition, the tetrahedral bond angles along the c-axis direction of the unit cell begin decreasing from 109.5° to 106.6 (7)°, which generates a "stretched" tetrahedral geometry. It is proposed that the Jahn-Teller effect at the tetrahedrally coordinated Fe2+ cation becomes active with compression and gives rise to the tetrahedral angular distortion, which in turn induces the cubic-to-tetragonal transition. A qualitative molecular orbital model is proposed to explain the origin and nature of the Jahn-Teller effect observed in this structure and its role in the pressure-induced phase transition.

    DOI: 10.1007/s00269-011-0468-6

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  • Pressure-composition phase diagram of the Pb(Mg1/3Nb2/3)O3-PbTiO3 solid solutions 査読 国際共著 国際誌

    M. Ahart, R. E. Cohen, R. J. Hemley, S. V. Sinogeikin, O. Shebanova, D. Ikuta, Z. G. Ye

    Proceedings of ISAF/PFM-2011   2011年9月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Institute of Electrical and Electronics Engineers  

    We combine high-pressure x-ray diffraction, high-pressure Raman scattering, and optical microscopic methods to investigate a series of PMN-xPT solid solutions (x=0.2, 0.3, 0.33, 0.35, 0.37, 0.4) in diamond anvil cells up to 20 GPa at 300 K. The Raman spectra show a new peak centered at 380 cm-1 above 6 GPa for all samples, consistent with previous observations. X-ray diffraction measurements are consistent with this spectral change indicating a structural phase transition. For example, we find that the triplet at the pseudocubic [220] Bragg peak merges into a doublet above 6 GPa. The analyzed results indicate that the morphotropic phase boundary (x=0.33 to 0.37) with monoclinic symmetry persists up to 7 GPa. The pressure dependence of ferroelectric domains in PMN-0.32PT single crystals was observed with a polarizing optical microscope. The domain wall density decreases with pressure and the domains disappears at modest pressure of 3 GPa. This indicates that the high pressure phase of PMN-PT is not a macroscopic polar state. We suggest a phase diagram for the PMN-xPT solid solutions.

    DOI: 10.1109/isaf.2011.6014105

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  • Diamond and other possible ultra-deep evidence discovered in the orogenic spinel-garnet peridotite from the Moldanubian zone of the Bohemian Massif, Czech Republic 査読 国際共著 国際誌

    K. Naemura, D. Ikuta, H. Kagi, S. Odake, T. Ueda, S. Ohi, T. Kobayashi, M. Svojtka, T. Hirajima

    Ultrahigh-Pressure Metamorphism   77 - 111   2011年3月

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    記述言語:英語   掲載種別:論文集(書籍)内論文   出版者・発行元:Elsevier  

    In the Plesovice peridotite, several lines of evidence suggesting an ultradeep condition are found. All of these facts suggest that the Plesovice peridotite once resided in the diamond-stability field, which could not be identified by the previous geothermobarometric studies. This suggests that diamond was stable in the rock before Stage I (high-temperature spinel6garnet peridotite stage), which is the oldest generation of mineral assemblage previously recognized in the Plesovice peridotite. Furthermore, the presence of pyroxene exsolution lamellae in the earlier generation of spinel (Stage I) implies the preexisting high-pressure stage before Stage I. If graphite in MS inclusions were originally crystallized as diamond, parental fluids responsible for MS inclusion was most likely entrapped in the host mineral before Stage I, and they should have crystallized daughter minerals during the cooling/exhumation trajectory from the diamond-stability field, through Stage I, to the chlorite peridotite stage. For MS inclusions within Spinel-I, there is a good possibility original fluid/melt was entrapped in the diamond-stability field, if host Spinel-I was originally its high-pressure polymorph, Ca-ferrite, or Ca-titanite. On the other hand, one could not find the typical pyroxene exsolution texture in garnet. This probably suggests that most garnet was secondary formed at the expense of Spinel-I at relatively low-pressure condition. Therefore, if graphite in garnet was originally diamond, it is most likely that the diamond was graphitized before the entrapment within garnet crystal.

    DOI: 10.1016/b978-0-12-385144-4.00002-3

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  • Superstructure of Challis mordenite with doubled monoclinic unit cell 査読 国際共著 国際誌

    N. Kawame, D. Ikuta, H. Kanazawa, K. Ito, M. E. Gunter, M. B. Boisen, O. Tamada

    American Mineralogist   92 ( 5-6 )   892 - 897   2007年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Mineralogical Society of America  

    A new superstructure was found in mordenite (Na5.59Ca1.80Al9.19Si38.81O96・nH2O) from Challis Valley, Idaho-a zeolite widely used in previous studies. The occurrence of the superstructure reflections were observed in 12 specimens from two rock samples, at the midpoint of layers in the oscillation photographs around the a* and b* axes, but not around the c* axis. The apparent 2a, 2b, and c axes are orthogonal. In spite of yielding an apparent orthorhombic cell, careful observation of the intensities revealed that the superstructure is monoclinic with twice the volume of the orthorhombic cell: a' = 27.356(9), b' = 27.356(9), c' = 7.517(2) A, γ' = 97.14(4)°, and V' = 5582(4) A3. The presence of the superstructure was examined for specimens from ten other localities and a synthetic sample but there was no evidence for extra spots of the superstructure, indicating that the occurrence is not common. The large displacement factors of O8 oxygen, and its associated 180° T-O-T angle that is energetically unfavorable, are basic to the mordenite structure. In the monoclinic superstructure the O8 oxygen is decomposed into several asymmetric O atoms by the symmetry reduction. The large displacement smearing of O8 oxygen perpendicular to the straight T-O-T, are explained by the superposition of decomposed O atoms. The extra spots are predominantly observed in the reciprocal planes with l = odd in the same way as diffuse streaks. The observation of extra spots and diffuse streaks suggests that there are three kinds of domains in the mordenite, one in the ordered form and two others in the random form of c/2 linear displacements. The domain in the ordered form represents the superstructure. Thus, we propose a model for the superstructure in which the c/2 displacement occurs alternatively in the two basic unit cells slightly modified in the superstructure, yielding the periodic arrangements.

    DOI: 10.2138/am.2007.2345

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  • First in situ x-ray identification of coesite and retrograde quartz on a glass thin section of an ultrahigh-pressure metamorphic rock and their crystal structure details 査読 国際共著 国際誌

    D. Ikuta, N. Kawame, S. Banno, T. Hirajima, K. Ito, J. F. Rakovan, R. T. Downs, O. Tamada

    American Mineralogist   92 ( 1 )   57 - 63   2007年1月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Mineralogical Society of America  

    To ensure the presence of coesite and its transformed polymorph, quartz, in ultrahigh-pressure (UHP) rocks and to examine the relic of the phase transformation, crystal structures were analyzed by single-crystal x-ray diffraction (XRD) directly using the rock thin section mounted on a slide glass. The rock sample used is a coesite-bearing eclogite from the Sulu UHP terrain, eastern China. The crystal structures were determined successfully by this new method and the presence of coesite and quartz in UHP rocks was identified for the first time by XRD. The R-factor [R(F)] converged to 0.046 for coesite and 0.087 for quartz. The displacement ellipsoids for coesite and quartz are larger than those previously reported for these two phases, which is consistent with expected effects of trapped strain due to the phase transformation from coesite to quartz during exhumation from the Earth's mantle. This paper is the first report of single-crystal XRD of a rock thin section on a glass slide and establishes the technique, and provides proof-of-concept of the method. Although the mineral species included in a thin section can often be identified by other methods, such as Raman spectroscopy, an advantage of the reported method is that it can be applied to any mineral in a thin section, and not just to the UHP minerals. Moreover, it is applicable to an unknown or new mineral in a thin section, discarding the spots of known minerals and constructing a lattice from the residual spots to find the structure of the unknown phase.

    DOI: 10.2138/am.2007.2228

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▼全件表示

MISC

  • Density deficit of the Earth's inner core revealed by a multi-megabar rhenium primary pressure scale 招待

    D. Ikuta, E. Ohtani, A. Q. R. Baron

    SPring-8/SACLA Research Frontiers   2023   102 - 103   2024年8月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:記事・総説・解説・論説等(大学・研究所紀要)   出版者・発行元:Japan Synchrotron Radiation Research Institute  

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  • Density deficit of the Earth's core revealed by a multi-megabar primary pressure scale 国際共著

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakamaki, R. Heid, D. Ishikawa, A. Q. R. Baron

    arXiv   2021   02076v3   2024年7月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:機関テクニカルレポート,技術報告書,プレプリント等   出版者・発行元:arXiv  

    An accurate pressure scale is a fundamental requirement to understand planetary interiors. Here, we establish a primary pressure scale extending to the multi-megabar pressures of the Earth's core, by combined measurement of the acoustic velocities and the density from a rhenium sample in a diamond anvil cell using inelastic x-ray scattering and x-ray diffraction. Our scale agrees well with previous primary scales and shock Hugoniots in each experimental pressure range, and reveals that previous scales have overestimated laboratory pressures by at least 20% at 230 gigapascals. It suggests that the light element content in the Earth's inner core (the density deficit relative to iron) is likely to be double what was previously estimated, or the Earth's inner core temperature is much higher than expected, or some combination thereof.

    DOI: 10.48550/arXiv.2104.02076

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  • Sound velocity of hexagonal close-packed iron to the Earth's inner core pressure 招待

    D. Ikuta, E. Ohtani, A. Q. R. Baron

    SPring-8/SACLA Research Frontiers   2022   106 - 107   2023年8月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:記事・総説・解説・論説等(大学・研究所紀要)   出版者・発行元:Japan Synchrotron Radiation Research Institute  

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講演・口頭発表等

  • IXS measurements in extreme pressure conditions and the implications for the Earth's core 招待 国際共著 国際会議

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakai, T. Sakamaki, R. Heid, D. Ishikawa, A. Q. R. Baron

    13th International Conference on Inelastic X-ray Scattering 

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    開催年月日: 2024年9月8日 - 2024年9月13日

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    開催地:Himeji, Hyogo  

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  • IXS measurements under extreme conditions: A multi-megabar primary pressure scale and the structure of the Earth's core 招待 国際会議

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakamaki, D. Ishikawa, A. Q. R. Baron

    Workshop on meV-Resolved Inelastic X-Ray Scattering 

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    開催年月日: 2021年9月6日 - 2021年9月9日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(指名)  

    開催地:Online  

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  • Sound velocity of B2-FeNiSi alloy at high pressure and high temperature and chemistry of the Earth's inner core

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakamaki, D. Ishikawa, A. Q. R. Baron

    65th High Pressure Conference of Japan 

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    開催年月日: 2024年11月13日 - 2024年11月15日

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:Morioka, Iwate  

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  • Sound velocity measurement of iron sulfide at high pressure and high temperature: Implications for light elements in the Earth's inner core

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakamaki, D. Ishikawa, A. Q. R. Baron

    65th High Pressure Conference of Japan 

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    開催年月日: 2024年11月13日 - 2024年11月15日

    記述言語:日本語   会議種別:ポスター発表  

    開催地:Morioka, Iwate  

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  • Sound velocity of B2 phase of Fe-Ni-Si alloys at high pressure and high temperature and constitution of the Earth's inner core

    E. Ohtani, D. Ikuta, H. Fukui, T. Sakamaki, D. Ishikawa, A. Q. R. Baron

    2024 Annual Meeting of Japan Association of Mineralogical Sciences 

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    開催年月日: 2024年9月12日 - 2024年9月14日

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:Nagoya, Aichi  

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  • Sound velocities of the hydrous iron-rich HH1-phase: Implication for the lower mantle seismic heterogeneities 国際共著 国際会議

    L. Liu, A. Q. R. Baron, E. Ohtani, H. Fukui, D. Ikuta, L. Zhang

    Japan Geosciecne Union Meeting 2024 

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    開催年月日: 2024年5月26日 - 2024年5月31日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Chiba  

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  • Sound velocity measurement for high-pressure phase of iron sulfide compounds at high pressure and high temperature 国際会議

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakamaki, D. Ishikawa, A. Q. R. Baron

    Japan Geosciecne Union Meeting 2024 

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    開催年月日: 2024年5月26日 - 2024年5月31日

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Chiba  

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  • Sound velocity measurements under extreme pressure conditions by inelastic x-ray scattering 招待

    D. Ikuta

    SPring-8 Users Community (SPRUC) Momentum-Resolved Spectroscopy Group Meeting FY2023 

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    開催年月日: 2024年3月1日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(指名)  

    開催地:Online  

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  • Sound velocity measurement of B2 Fe-Ni-Si alloys at high pressure and high temperature 国際会議

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakamaki, I. Mashino, D. Ishikawa, A. Q. R. Baron

    Japan Geosciecne Union Meeting 2023 

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    開催年月日: 2023年5月21日 - 2023年5月26日

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Chiba  

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  • Deformation experiments on NaNiF3 perovskite and post-perovskite 国際会議

    D. Yamazaki, D. Ikuta, K. Lau, C. Liu, T. Yoshino, N. Tsujino, S. Kakizawa, Y. Higo, Y. Nishihara

    Japan Geosciecne Union Meeting 2023 

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    開催年月日: 2023年5月21日 - 2023年5月26日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Chiba  

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  • Sound velocity measurement of iron alloys and rhenium by inelastic x-ray scattering under high pressure: Implications to the Earth's interior

    E. Ohtani, D. Ikuta, H. Fukui, T. Sakamaki, I. Mashino, T. Sakai, D. Ishikawa, A. Q. R. Baron

    63rd High Pressure Conference of Japan 

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    開催年月日: 2022年12月13日 - 2022年12月15日

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:Ibaraki, Osaka  

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  • Sound velocity measurement of hcp-iron to the Earth's inner core pressure: Implications for light elements in the inner core

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakai, D. Ishikawa, A. Q. R. Baron

    63rd High Pressure Conference of Japan 

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    開催年月日: 2022年12月13日 - 2022年12月15日

    記述言語:日本語   会議種別:ポスター発表  

    開催地:Ibaraki, Osaka  

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  • Sound velocity of hcp-iron to the inner core pressure, and light elements in the inner core

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakai, D. Ishikawa, A. Q. R. Baron

    2022 Annual Meeting of Japan Association of Mineralogical Sciences 

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    開催年月日: 2022年9月17日 - 2022年9月19日

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:Niigata  

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  • Density deficit of Earth's inner core revealed by a new rhenium primary pressure scale 国際会議

    E. Ohtani, D. Ikuta, H. Fukui, T. Sakamaki, D. Ishikawa, A. Q. R. Baron

    Japan Geosciecne Union Meeting 2022 

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    開催年月日: 2022年5月22日 - 2022年6月3日

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Chiba  

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  • Sound velocity measurement of hcp-iron above 3 megabar with a new type diamond anvil cell 国際会議

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakai, D. Ishikawa, A. Q. R. Baron

    Japan Geosciecne Union Meeting 2022 

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    開催年月日: 2022年5月22日 - 2022年6月3日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Chiba  

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  • Sound velocity of hcp-iron to the Earth's inner core pressure: Implication for light elements in the core 国際会議

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakai, D. Ishikawa, A. Q. R. Baron

    Japan Geosciecne Union Meeting 2022 

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    開催年月日: 2022年5月20日 - 2022年6月3日

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Chiba  

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  • Water partition between hydrous and anhydrous minerals under high temperature and high pressure and the role of water in the Earth's interior 国際共著

    E. Ohtani, T. Ishii, A. Shatskiy, D. Ikuta

    62nd High Pressure Conference of Japan 

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    開催年月日: 2021年10月18日 - 2021年10月20日

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:Himeji, Hyogo  

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  • Primary pressure scale of rhenium to multi-megabar pressures by inelastic x-ray scattering

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakamaki, D. Ishikawa, A. Q. R. Baron

    62nd High Pressure Conference of Japan 

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    開催年月日: 2021年10月18日 - 2021年10月20日

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:Himeji, Hyogo  

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  • Determination for compressional wave velocity of hcp-iron to multi-megabar pressures by inelastic x-ray scattering

    D. Ikuta, E. Ohtani, H. Fukui, D. Ishikawa, A. Q. R. Baron

    62nd High Pressure Conference of Japan 

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    開催年月日: 2021年10月18日 - 2021年10月20日

    記述言語:日本語   会議種別:ポスター発表  

    開催地:Himeji, Hyogo  

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  • Density deficit of Earth's inner core revealed by a multi-megabar rhenium pressure scale

    D. Ikuta, E. Ohtani, H. Fukui, T. Sakamaki, D. Ishikawa, A. Q. R. Baron

    2021 Annual Meeting of Japan Association of Mineralogical Sciences 

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    開催年月日: 2021年9月16日 - 2021年9月18日

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:Online  

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  • Existence of the two-phase mixture of HCP and B2 phases in the inner core 国際共著 国際会議

    E. Ohtani, D. Ikuta, S. Dominijanni, C. A. McCammon, N. Hirao, H. Fukui, H. Uchiyama, A. Q. R. Baron

    Japan Geosciecne Union Meeting 2021 

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    開催年月日: 2021年5月30日 - 2021年6月6日

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Online  

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  • Sound velocity of hcp-iron at extreme pressure by inelastic x-ray scattering measurement 国際会議

    D. Ikuta, E. Ohtani, H. Fukui, D. Ishikawa, A. Q. R. Baron

    Japan Geosciecne Union Meeting 2021 

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    開催年月日: 2021年5月30日 - 2021年6月6日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Online  

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  • Sound velocity measurements of B2-Fe-Ni-Si alloy under high pressure by inelastic x-ray scattering: Implications for the composition of Earth's core 国際共著 国際会議

    S. Dominijanni, C. A. McCammon, E. Ohtani, D. Ikuta, T. Sakamaki, T. Ishii, G. Criniti, L. S. Dubrovinsky, S. Khandarkhaeva, T. Fedotenko, K. Glazyrin, H. Uchiyama, H. Fukui, A. Q. R. Baron

    17th International Symposium on Experimental Mineralogy, Petrology and Geochemistry 

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    開催年月日: 2021年3月1日 - 2021年3月3日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:Online  

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  • Sound velocity of B2-FeNiSi alloy at high pressure determined with inelastic x-ray scattering: Implications for the composition of the Earth's inner core 国際共著 国際会議

    S. Dominijanni, E. Ohtani, D. Ikuta, T. Sakamaki, H. Fukui, C. McCammon, L. Dubrovinsky, H. Uchiyama, A. Q. R. Baron

    Japan Geosciecne Union - American Geophysical Union Joint Meeting 2020 

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    開催年月日: 2020年7月12日 - 2020年7月16日

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Online  

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  • Sound velocity measurement of Fe-Ni-Si alloys at high pressure and high temperature 国際会議

    D. Ikuta, E. Ohtani, H. Fukui, H. Uchiyama, S. Tsutsui, A. Q. R. Baron

    Japan Geosciecne Union - American Geophysical Union Joint Meeting 2020 

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    開催年月日: 2020年7月12日 - 2020年7月16日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Online  

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  • Composition of the Earth's inner core from high pressure sound velocity measurements of Fe-Ni-Si alloys 国際共著 国際会議

    S. Dominijanni, C. McCammon, E. Ohtani, D. Ikuta, T. Sakamaki, T. Ishii

    European Geosciences Union General Assembly 2020 

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    開催年月日: 2020年5月3日 - 2020年5月8日

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Online  

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  • Inner core as a two phase mixture of the Fe-Ni-Si alloys 国際会議

    E. Ohtani, D. Ikuta, N. Hirao, T. Sakamaki

    2019 American Geophysical Union Fall Meeting 

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    開催年月日: 2019年12月9日 - 2019年12月13日

    記述言語:英語   会議種別:ポスター発表  

    開催地:San Francisco  

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  • Sound velocity measurement of Fe-Ni-Si alloys at high pressure and high temperature

    D. Ikuta, E. Ohtani, T. Sakamaki, H. Fukui, H. Uchiyama, S. Tsutsui, A. Q. R. Baron

    60th High Pressure Conference of Japan 

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    開催年月日: 2019年10月23日 - 2019年10月25日

    記述言語:日本語   会議種別:ポスター発表  

    開催地:Sapporo, Hokkaido  

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  • Sound velocity and Mossbauer spectroscopy measurements of FeH2

    D. Ikuta, E. Ohtani, S. Kawaguchi-Imada, N. Hirao, Y. Ohishi

    2019 Annual Meeting of Japan Association of Mineralogical Sciences 

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    開催年月日: 2019年9月20日

    記述言語:日本語   会議種別:ポスター発表  

    開催地:Fukuoka  

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  • Inelastic x-ray scattering at extreme conditions and its geophysical applications 招待 国際会議

    E. Ohtani, T. Sakamaki, H. Fukui, D. Ikuta, D. Ishikawa, H. Uchiyama, S. Tsutsui, A. Q. R. Baron

    11th International Conference on Inelastic X-ray Scattering 

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    開催年月日: 2019年6月23日 - 2019年6月28日

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    開催地:Stony Brook  

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  • Phase relations in the Fe-Ni-Si system at high pressures and high temperatures 国際会議

    D. Ikuta, E. Ohtani, S. Kawaguchi-Imada, N. Hirao, Y. Ohishi

    Japan Geosciecne Union Meeting 2019 

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    開催年月日: 2019年5月26日 - 2019年5月30日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Chiba  

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  • Ultralow-velocity zones possibly explained by light element-enriched iron compounds 国際共著 国際会議

    L. Yuan, E. Ohtani, X. Wu, S. Huang, D. Ikuta, T. Sakamaki, S. Kamada, H. Fukui, S. Tsutsui, H. Uchiyama, D. Ishikawa, N. Hirao, A. Q. R. Baron

    Japan Geosciecne Union Meeting 2019 

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    開催年月日: 2019年5月26日 - 2019年5月30日

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Chiba  

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  • B2 phase in the inner core: Constraints from high pressure experiments 国際会議

    E. Ohtani, D. Ikuta, S. Kamada, T. Sakamaki, N. Hirao

    Japan Geosciecne Union Meeting 2019 

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    開催年月日: 2019年5月26日 - 2019年5月30日

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Chiba  

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  • Role of water on dynamics in the lower mantle and core-mantle boundary regions 国際共著 国際会議

    E. Ohtani, T. Ishii, L. Yuan, D. Ikuta, T. Katsura, D. Frost

    Japan Geosciecne Union Meeting 2019 

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    開催年月日: 2019年5月26日 - 2019年5月30日

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Chiba  

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  • Fe2O3 post-perovskite as a candidate phase for ultralow-velocity zones 国際共著 国際会議

    L. Yuan, E. Ohtani, X. Wu, S. Huang, D. Ikuta, T. Sakamaki, S. Kamada, H. Fukui, S. Tsutsui, H. Uchiyama, D. Ishikawa, N. Hirao, A. Q. R. Baron

    European Geosciences Union General Assembly 2019 

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    開催年月日: 2019年4月7日 - 2019年4月12日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Vienna  

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  • In-situ high pressure and temperature neutron diffraction study of the Fe-H system and hydrogen in the planetary core 国際会議

    E. Ohtani, D. Ikuta, A. Sano-Furukawa, Y. Shibazaki, H. Terasaki, L. Yuan, T. Hattori

    2018 American Geophysical Union Fall Meeting 

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    開催年月日: 2018年12月10日 - 2018年12月14日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Washington, D.C.  

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  • Sound velocity measurement of rhenium at extreme pressure conditions by inelastic x-ray scattering

    D. Ikuta, E. Ohtani, T. Sakamaki, H. Fukui, D. Ishikawa, A. Q. R. Baron

    59th High Pressure Conference of Japan 

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    開催年月日: 2018年11月26日 - 2018年11月28日

    記述言語:日本語   会議種別:ポスター発表  

    開催地:Okayama  

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  • Phase relations in the Fe-Ni-Si system at high pressure and high temperature

    D. Ikuta, E. Ohtani, S. Kawaguchi-Imada, N. Hirao, Y. Ohishi

    2018 Annual Meeting of Japan Association of Mineralogical Sciences 

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    開催年月日: 2018年9月19日 - 2018年9月21日

    記述言語:日本語   会議種別:ポスター発表  

    開催地:Yamagata  

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  • Chemical reactions between Fe and H2O up to megabar pressures and implications for water storage in the Earth's mantle and core 国際会議

    L. Yuan, E. Ohtani, D. Ikuta, S. Kamada, J. Tsuchiya, N. Hirao, Y. Ohishi, A. Suzuki

    Japan Geosciecne Union Meeting 2018 

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    開催年月日: 2018年5月20日 - 2018年5月24日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Chiba  

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  • Pressure-volume-temperature behaviors of iron hydride at high pressure and high temperature based on neutron diffraction study

    D. Ikuta, E. Ohtani, A. Sano-Furukawa, Y. Shibazaki, H. Terasaki, L. Yuan, T. Hattori

    58th High Pressure Conference of Japan 

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    開催年月日: 2017年11月8日 - 2017年11月10日

    記述言語:日本語   会議種別:ポスター発表  

    開催地:Nagoya, Aichi  

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  • Sound velocity of iron-light element compounds and composition of the inner core 国際会議

    E. Ohtani, T. Sakamaki, S. Kamada, D. Ikuta, R. Tanaka, H. Fukui, A. Q. R. Baron

    9th High-Pressure Mineral Physics Seminar 

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    開催年月日: 2017年9月24日 - 2017年9月28日

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Saint Malo  

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  • Pressure-volume-temperature behaviors for hydrogen content and volume in iron hydride at high pressure and high temperature 国際会議

    D. Ikuta, E. Ohtani, A. Sano-Furukawa, Y. Shibazaki, H. Terasaki, L. Yuan, T. Hattori

    9th High-Pressure Mineral Physics Seminar 

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    開催年月日: 2017年9月24日 - 2017年9月28日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Saint Malo  

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  • Inner core composition estimated by the sound velocity and solid-liquid partitioning

    E. Ohtani, T. Sakamaki, D. Ikuta, R. Tanaka, H. Fukui, A. Q. R. Baron

    2017 Annual Meeting of Japan Association of Mineralogical Sciences 

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    開催年月日: 2017年9月12日 - 2017年9月14日

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:Matsuyama, Ehime  

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  • Pressure-volume-temperature behaviors for hydrogen content and volume in iron hydride at high pressure and high temperature

    D. Ikuta, E. Ohtani, A. Sano-Furukawa, Y. Shibazaki, H. Terasaki, L. Yuan, T. Hattori

    2017 Annual Meeting of Japan Association of Mineralogical Sciences 

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    開催年月日: 2017年9月12日 - 2017年9月14日

    記述言語:日本語   会議種別:ポスター発表  

    開催地:Matsuyama, Ehime  

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  • Pressure-volume-temperature relations for hydrogen volume and content in iron hydride at high pressure and high temperature 国際会議

    D. Ikuta, A. Sano-Furukawa, Y. Shibazaki, H. Terasaki, L. Yuan, T. Hattori, E. Ohtani

    Japan Geosciecne Union - American Geophysical Union Joint Meeting 2017 

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    開催年月日: 2017年5月20日 - 2017年5月28日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Chiba  

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  • Magnetic phase diagrams and thermal equations of state of Fe7C3 and Fe3C up to the pressure-temperature conditions of Earth's core 国際共著 国際会議

    J. Liu, Z. Li, B. Chen, J. Li, D. Ikuta, J. Smith, S. Sinogeikin, D. Popov, C. Kenney-Benson

    2015 American Geophysical Union Fall Meeting 

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    開催年月日: 2015年12月14日 - 2015年12月18日

    記述言語:英語   会議種別:ポスター発表  

    開催地:San Francisco  

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  • Viscosity of liquids sulfur and selenium at high pressures and high temperatures and their correlations with liquid structure 国際共著 国際会議

    D. Ikuta, Y. Kono, L. Lei, C. Kenney-Benson, Y. Wang, G. Shen

    2015 American Geophysical Union Fall Meeting 

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    開催年月日: 2015年12月14日 - 2015年12月18日

    記述言語:英語   会議種別:ポスター発表  

    開催地:San Francisco  

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  • “Invar”-like behavior in compressed Fe7C3 with implication for deep carbon cycle 国際共著 国際会議

    J. Liu, J. Li, D. Ikuta

    2014 American Geophysical Union Fall Meeting 

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    開催年月日: 2014年12月15日 - 2014年12月19日

    記述言語:英語   会議種別:ポスター発表  

    開催地:San Francisco  

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  • High pressure collaborative access team at the Advanced Photon Source: An integrated facility for high pressure research 国際共著 国際会議

    G. Boman, L. Bai, A. Bommannavar, P. Chow, R. Hrubiak, F. Humble, D. Ikuta, C. Kenney-Benson, Y. Kono, C. Lin

    HPCAT Workshop on High-Pressure Time-Resolved Synchrotron Techniques 

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    開催年月日: 2014年9月25日 - 2014年9月27日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(指名)  

    開催地:Argonne  

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  • HPCAT 16-BMD: the micro-XRD and XANES beamline for high-pressure research 国際共著 国際会議

    C. Park, D. Popov, D. Ikuta, C. Lin, C. Kenney-Benson, E. Rod, G. Shen

    HPCAT Workshop on High-Pressure Time-Resolved Synchrotron Techniques 

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    開催年月日: 2014年9月25日 - 2014年9月27日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(指名)  

    開催地:Argonne  

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  • Combined XRD-XANES at 16BM-D 国際共著 国際会議

    C. Park, E. Rod, C. Kenney-Benson, D. Popov, D. Ikuta, L. Bai, W. Yang, G. Shen

    HPCAT Workshop on Advances in Matter under Extreme Conditions 

     詳細を見る

    開催年月日: 2012年10月10日 - 2012年10月12日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(指名)  

    開催地:Argonne  

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  • High-resolution powder x-ray diffraction at 16BM-D 国際共著 国際会議

    C. Park, C. Kenney-Benson, D. Popov, P. Dera, D. Ikuta, L. Bai, G. Shen

    HPCAT Workshop on Advances in Matter under Extreme Conditions 

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    開催年月日: 2012年10月10日 - 2012年10月12日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(指名)  

    開催地:Argonne  

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  • Pressure effects on relaxor ferroelectrics 国際共著 国際会議

    M. Ahart, S. Kojima, S. V. Sinogeikin, D. Ikuta, H. K. Mao, R. Yang, Z. G. Ye, R. J. Hemley

    HPCAT Workshop on Advances in Matter under Extreme Conditions 

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    開催年月日: 2012年10月10日 - 2012年10月12日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:Argonne  

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  • Experimental and optical stations at HPCAT 国際共著 国際会議

    G. Boman, A. Bommannavar, P. Chow, D. Ikuta, C. Kenney-Benson, Y. Kono, H. K. Mao, Y. Meng, C. Park, D. Popov

    HPCAT Workshop on Advances in Matter under Extreme Conditions 

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    開催年月日: 2012年10月10日 - 2012年10月12日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(指名)  

    開催地:Argonne  

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  • High pressure collaborative access team at the Advanced Photon Source: An integrated facility for high pressure research 国際共著 国際会議

    G. Boman, A. Bommannavar, P. Chow, D. Ikuta, C. Kenney-Benson, Y. Kono, H. K. Mao, Y. Meng, V. O’Connor, C. Park

    HPCAT Workshop on Advances in Matter under Extreme Conditions 

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    開催年月日: 2012年10月10日 - 2012年10月12日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(指名)  

    開催地:Argonne  

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  • High pressure diffraction and XANES studies on tyrrellite 国際共著 国際会議

    K. Kothapalli, F. Nasreen, L. Bai, C. Park, D. Popov, D. Ikuta, B. Lavina, Y. Zhao

    HPCAT Workshop on Advances in Matter under Extreme Conditions 

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    開催年月日: 2012年10月10日 - 2012年10月12日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:Argonne  

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  • High pressure single-crystal x-ray diffraction study of CoS2 at room temperature 国際共著 国際会議

    L. Bai, X. Lu, M. Pravica, Y. Zhao, D. Ikuta, D. Popov, C. Park, G. Shen

    HPCAT Workshop on Advances in Matter under Extreme Conditions 

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    開催年月日: 2012年10月10日 - 2012年10月12日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:Argonne  

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  • Single-crystal x-ray diffraction study at HPCAT 16BM-D beamline 国際共著 国際会議

    D. Ikuta, G. Shen, S. V. Sinogeikin, S. D. Jacobsen

    HPCAT Workshop on Advances in Matter under Extreme Conditions 

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    開催年月日: 2012年10月10日 - 2012年10月12日

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:Argonne  

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  • Single-crystal x-ray diffraction study of (Mg, Fe)O at high pressures 国際共著 国際会議

    D. Ikuta, G. Shen, S. V. Sinogeikin, S. D. Jacobsen

    IUCrHP2012/QuBS2012 

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    開催年月日: 2012年9月23日 - 2012年9月27日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Mito, Ibaraki  

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  • Anharmonicity and bonding electrons in silicon under high pressures 国際共著 国際会議

    G. Shen, D. Ikuta

    American Physical Society March Meeting 2012 

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    開催年月日: 2012年2月27日 - 2012年3月2日

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Boston  

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  • The influence of the Jahn-Teller effect at Fe2+ on the structure of chromite at high pressure 国際共著 国際会議

    A. Kyono, S. A. Gramsch, T. Yamanaka, D. Ikuta, M. Ahart, B. O. Mysen, H. K. Mao, R. J. Hemley

    International Union of Crystallography XXII Congress 

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    開催年月日: 2011年8月20日 - 2011年8月30日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Madrid  

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  • Diamond and other mineralogical records of very deep origin in spinel-garnet peridotite from Moldanubian Zone, Bohemian Massif 招待 国際共著 国際会議

    K. Naemura, D. Ikuta, H. Kagi, S. Odake, T. Ueda, S. Ohi, T. Kobayashi, T. Hirajima, M. Svojtka

    2010 American Geophysical Union Fall Meeting 

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    開催年月日: 2010年12月13日 - 2010年12月17日

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    開催地:San Francisco  

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  • The variety of the mode of the occurrence of the Al2SiO5 polymorph in the Gfohl granulite 国際共著

    T. Hirajima, H. Sai, H. Hisashima, T. Kobayashi, D. Ikuta, O. Tamada, Y. Hiroi, M. Svojtka

    113th Annual Meeting of the Geological Society of Japan 

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    開催年月日: 2006年9月16日 - 2006年9月18日

    記述言語:日本語   会議種別:ポスター発表  

    開催地:Kochi  

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  • New monoclinic superstructure of mordenite with 2a x 2b x c cell 国際共著 国際会議

    N. Kawame, D. Ikuta, H. Kanazawa, K. Ito, M. E. Gunter, M. B. Boisen, O. Tamada

    19th General Meeting of the International Mineralogical Association 

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    開催年月日: 2006年7月23日 - 2006年7月28日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Kobe, Hyogo  

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  • First in situ x-ray identification of coesite and retrograde quartz on a glass thin section of an ultrahigh-pressure metamorphic rock and their crystal structure details 国際共著 国際会議

    D. Ikuta, N. Kawame, S. Banno, T. Hirajima, K. Ito, J. F. Rakovan, R. T. Downs, O. Tamada

    19th General Meeting of the International Mineralogical Association 

     詳細を見る

    開催年月日: 2006年7月23日 - 2006年7月28日

    記述言語:英語   会議種別:ポスター発表  

    開催地:Kobe, Hyogo  

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▼全件表示

共同研究・競争的資金等の研究

  • 非弾性X線散乱法による固体金属の高温高圧絶対圧力スケール構築と地球科学への適用

    研究課題/領域番号:24K00734  2024年04月 - 2028年03月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    D. Ikuta, E. Ohtani, H. Fukui

      詳細を見る

    担当区分:研究代表者  資金種別:競争的資金

    配分額:18070000円 ( 直接経費:13900000円 、 間接経費:4170000円 )

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  • 超高圧高温における鉄合金の弾性波速度・状態方程式の測定による内核の不均質性の解明

    研究課題/領域番号:24K00722  2024年04月 - 2028年03月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    E. Ohtani, D. Ikuta, T. Sakamaki, T. Ishii, H. Fukui, A. Q. R. Baron

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    担当区分:研究分担者  資金種別:競争的資金

    配分額:17940000円 ( 直接経費:13800000円 、 間接経費:4140000円 )

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  • 地球核領域での絶対圧力スケールの構築 国際共著

    研究課題/領域番号:20H00187  2020年04月 - 2023年03月

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    E. Ohtani, T. Sakamaki, H. Fukui, M. Miyahara, A. Q. R. Baron

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    資金種別:競争的資金

    配分額:44070000円 ( 直接経費:33900000円 、 間接経費:10170000円 )

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  • 地球核の最適モデルの創出 国際共著

    研究課題/領域番号:15H05748  2015年05月 - 2020年03月

    日本学術振興会  科学研究費助成事業  基盤研究(S)

    E. Ohtani, T. Sakamaki, N. Hirao, H. Fukui, M. Miyahara, A. Suzuki

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    資金種別:競争的資金

    配分額:194610000円 ( 直接経費:149700000円 、 間接経費:44910000円 )

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  • X線による超高圧変成岩鉱物の研究 国際共著

    2003年 - 2008年

    京都大学 人間・環境学研究科 相関環境学専攻 

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