start-ver=1.4 cd-journal=joma no-vol=6 cd-vols= no-issue= article-no= start-page=217 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2018 dt-pub=20181129 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Impurity Resistivity of fcc and hcp Fe-Based Alloys: Thermal Stratification at the Top of the Core of Super-Earths en-subtitle= kn-subtitle= en-abstract= kn-abstract= It is widely known that the Earth's Fe dominant core contains a certain amount of light elements such as H, C, N, O, Si, and S. We report the results of first-principles calculations on the band structure and the impurity resistivity of substitutionally disordered hcp and fcc Fe based alloys. The calculation was conducted by using the AkaiKKR (machikaneyama) package, which employed the Korringa-Kohn-Rostoker (KKR) method with the atomic sphere approximation (ASA). The local density approximation (LDA) was adopted for the exchange-correlation potential. The coherent potential approximation (CPA) was used to treat substitutional disorder effect. The impurity resistivity is calculated from the Kubo-Greenwood formula with the vertex correction. In dilute alloys with 1 at. % impurity concentration, calculated impurity resistivities of C, N, O, S are comparable to that of Si. On the other hand, in concentrated alloys up to 30 at. %, Si impurity resistivity is the highest followed by C impurity resistivity. Ni impurity resistivity is the smallest. N, O, and S impurity resistivities lie between Si and Ni. Impurity resistivities of hcp-based alloys show systematically higher values than fcc alloys. We also calculated the electronic specific heat from the density of states (DOS). For pure Fe, the results show the deviation from the Sommerfeld value at high temperature, which is consistent with previous calculation. However, the degree of deviation becomes smaller with increasing impurity concentration. The violation of the Sommerfeld expansion is one of the possible sources of the violation of the Wiedemann-Franz law, but the present results could not resolve the inconsistency between recent electrical resistivity and thermal conductivity measurements. Based on the present thermal conductivity model, we calculated the conductive heat flux at the top of terrestrial cores, which is comparable to the heat flux across the thermal boundary layer at the bottom of the mantle. This indicates that the thermal stratification may develop at the top of the liquid core of super-Earths, and hence, chemical buoyancies associated with the inner core growth and/or precipitations are required to generate the global magnetic field through the geodynamo. en-copyright= kn-copyright= en-aut-name=GomiHitoshi en-aut-sei=Gomi en-aut-mei=Hitoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= en-keyword=band structure kn-keyword=band structure en-keyword=density of states kn-keyword=density of states en-keyword=electrical resistivity kn-keyword=electrical resistivity en-keyword=thermal conductivity kn-keyword=thermal conductivity en-keyword=Linde's rule kn-keyword=Linde's rule en-keyword=KKR-CPA kn-keyword=KKR-CPA END start-ver=1.4 cd-journal=joma no-vol=103 cd-vols= no-issue=8 article-no= start-page=1271 end-page=1281 dt-received= dt-revised= dt-accepted= dt-pub-year=2018 dt-pub=20180801 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=The effects of ferromagnetism and interstitial hydrogen on the equation of states of hcp and dhcp FeHx: Implications for the Earth's inner core age en-subtitle= kn-subtitle= en-abstract= kn-abstract= Hydrogen has been considered as an important candidate of light elements in the Earth's core. Because iron hydrides are unquenchable, hydrogen content is usually estimated from in situ X-ray diffraction measurements that assume the following linear relation: x = (V-FeHx - V-Fe)/Delta V-H, where x is the hydrogen content, Delta V-H is the volume expansion caused by unit concentration of hydrogen, and V-FeHx and V-Fe are volumes of FeHx and pure iron, respectively. To verify the linear relationship, we computed the equation of states of hexagonal iron with interstitial hydrogen by using the Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA). The results indicate a discontinuous volume change at the magnetic transition and almost no compositional (x) dependence in the ferromagnetic phase at 20 GPa, whereas the linearity is confirmed in the non-magnetic phase. In addition to their effect on the density-composition relationship in the Fe-FeHx system, which is important for estimating the hydrogen incorporation in planetary cores, the magnetism and interstitial hydrogen also affect the electrical resistivity of FeHx. The thermal conductivity can be calculated from the electrical resistivity by using the Wiedemann-Franz law, which is a critical parameter for modeling the thermal evolution of the Earth. Assuming an Fe1-ySiyHx ternary outer core model (0.0 <= x <= 0.7), we calculated the thermal conductivity and the age of the inner core. The resultant thermal conductivity is similar to 100 W/m/K and the maximum inner core age ranges from 0.49 to 0.86 Gyr. en-copyright= kn-copyright= en-aut-name=GomiHitoshi en-aut-sei=Gomi en-aut-mei=Hitoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=FeiYingwei en-aut-sei=Fei en-aut-mei=Yingwei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Geophysical Laboratory, Carnegie Institution of Washington kn-affil= affil-num=3 en-affil=Institute for Planetary Materials, Okayama University kn-affil= en-keyword=FeHx kn-keyword=FeHx en-keyword=ferromagnetism kn-keyword=ferromagnetism en-keyword=chemical disorder kn-keyword=chemical disorder en-keyword=equation of states kn-keyword=equation of states en-keyword=KKR-CPA kn-keyword=KKR-CPA END start-ver=1.4 cd-journal=joma no-vol=100 cd-vols= no-issue=21 article-no= start-page=214302 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=20191205 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Resistivity, Seebeck coefficient, and thermal conductivity of platinum at high pressure and temperature en-subtitle= kn-subtitle= en-abstract= kn-abstract= Platinum (Pt) is one of the most widely used functional materials for high-pressure and high-temperature experiments. Despite the crucial importance of its transport properties, both experimental and theoretical studies are very limited. In this study, we conducted density functional theory calculations on the electrical resistivity, the Seebeck coefficient, and the thermal conductivity of solid face-centered cubic Pt at pressures up to 200 GPa and temperatures up to 4800 K by using the Kubo-Greenwood formula. The thermal lattice displacements were treated within the alloy analogy, which is represented by means of the Korringa-Kohn-Rostoker method with the coherent potential approximation. The electrical resistivity decreases with pressure and increases with temperature. These two conflicting effects yield a constant resistivity of similar to 70 mu Omega cm along the melting curve. Both pressure and temperature effects enhance the thermal conductivity at low temperatures, but the temperature effect becomes weaker at high temperatures. Although the pressure dependence of the Seebeck coefficient is negligibly small at temperatures below similar to 1500 K, it becomes larger at higher temperatures. It requires a calibration of a thermocouple such as Pt-Rh in high-pressure and -temperature experiments. en-copyright= kn-copyright= en-aut-name=GomiHitoshi en-aut-sei=Gomi en-aut-mei=Hitoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=530 cd-vols= no-issue= article-no= start-page=115887 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=20191023 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Grain boundary diffusion of W in lower mantle phase with implications for isotopic heterogeneity in oceanic island basalts by core-mantle interactions en-subtitle= kn-subtitle= en-abstract= kn-abstract=Tungsten isotopes provide important constraints on the ocean-island basalt (OIB) source regions. Recent analyses of ƒÊ182W in modern basalts with high 3He/4He originating from the core-mantle boundary region reveal two distinct features: positive ƒÊ182W in Phanerozoic flood basalts indicating the presence of primordial reservoir, and negative ƒÊ182W in modern OIBs. One possibility to produce large variations in ƒÊ182W is interaction between the mantle and outer core. Here, we report grain boundary diffusion of W in lower mantle phases. High pressure experimental results show that grain boundary diffusion of W is fast and strongly temperature dependent. Over Earth's history, diffusive transport of W from the core to the lowermost mantle may have led to significant modification of the W isotopic composition of the lower mantle at length scales exceeding one kilometer. Such grain boundary diffusion can lead to large variations in ƒÊ182W in modern basalts as a function of the distance of their source regions from the core mantle boundary. Modern oceanic island basalts from Hawaii, Samoa and Iceland exhibit negative ƒÊ182W and likely originated from the modified isotope region just above the core-mantle boundary, whereas those with positive ƒÊ182W could be derived from the thick Large Low Shear Velocity Provinces (LLSVPs) far from the core-mantle boundary (CMB). When highly-oxidized slabs accumulate at the CMB oxidizing the outer core at the interface, a large W flux with negative ƒÊ182W can be added to the silicate mantle. As a result, the source region of the OIB would be effectively modified to a negative ƒÊ182W. en-copyright= kn-copyright= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=MakinoYoshiki en-aut-sei=Makino en-aut-mei=Yoshiki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=SuzukiToshihiro en-aut-sei=Suzuki en-aut-mei=Toshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=HirataTakafumi en-aut-sei=Hirata en-aut-mei=Takafumi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Geochemical Research Center, The University of Tokyo kn-affil= affil-num=3 en-affil=Geochemical Research Center, The University of Tokyo kn-affil= affil-num=4 en-affil=Geochemical Research Center, The University of Tokyo kn-affil= en-keyword=core mantle interaction kn-keyword=core mantle interaction en-keyword=grain boundary diffusion kn-keyword=grain boundary diffusion en-keyword=high pressure experiment kn-keyword=high pressure experiment en-keyword=postspinel kn-keyword=postspinel en-keyword=W isotope kn-keyword=W isotope en-keyword=core mantle boundary kn-keyword=core mantle boundary END start-ver=1.4 cd-journal=joma no-vol=91 cd-vols= no-issue=3 article-no= start-page=035115 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20200319 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Measurement of the Seebeck coefficient under high pressure by dual heating en-subtitle= kn-subtitle= en-abstract= kn-abstract=This study presents a new method for measuring the Seebeck coefficient under high pressure in a multi-anvil apparatus. The application of a dual-heating system enables precise control of the temperature difference between both ends of the sample in a high-pressure environment. Two pairs of W?Re thermocouples were employed at both ends of the sample to monitor and control the temperature difference, and independent probes were arranged to monitor the electromotive force (emf) produced by temperature oscillation at a given target temperature. The temperature difference was controlled within 1 K during the resistivity measurements to eliminate the influence of the emf owing to a sample temperature gradient. The Seebeck measurement was successfully measured from room temperature to 1400 K and was obtained by averaging the two measured values with opposite thermal gradient directions (?20 K). Thermoelectric properties were measured on disk-shaped p-type Si wafers with two different carrier concentrations as a reference for high Seebeck coefficients. This method is effective to determine the thermoelectric power of materials under pressure. en-copyright= kn-copyright= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=WangRan en-aut-sei=Wang en-aut-mei=Ran kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=GomiHitoshi en-aut-sei=Gomi en-aut-mei=Hitoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=MoriYoshihisa en-aut-sei=Mori en-aut-mei=Yoshihisa kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=4 en-affil=3Department of Applied Science, Okayama University of Science kn-affil= END start-ver=1.4 cd-journal=joma no-vol=14 cd-vols= no-issue=19 article-no= start-page=5476 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2021 dt-pub=20210922 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Electrical Resistivity of Cu and Au at High Pressure above 5 GPa: Implications for the Constant Electrical Resistivity Theory along the Melting Curve of the Simple Metals en-subtitle= kn-subtitle= en-abstract= kn-abstract=The electrical resistivity of solid and liquid Cu and Au were measured at high pressures from 6 up to 12 GPa and temperatures & SIM;150 K above melting. The resistivity of the metals was also measured as a function of pressure at room temperature. Their resistivity decreased and increased with increasing pressure and temperature, respectively. With increasing pressure at room temperature, we observed a sharp reduction in the magnitude of resistivity at & SIM;4 GPa in both metals. In comparison with 1 atm data and relatively lower pressure data from previous studies, our measured temperature-dependent resistivity in the solid and liquid states show a similar trend. The observed melting temperatures at various fixed pressure are in reasonable agreement with previous experimental and theoretical studies. Along the melting curve, the present study found the resistivity to be constant within the range of our investigated pressure (6-12 GPa) in agreement with the theoretical prediction. Our results indicate that the invariant resistivity theory could apply to the simple metals but at higher pressure above 5 GPa. These results were discussed in terms of the saturation of the dominant nuclear screening effect caused by the increasing difference in energy level between the Fermi level and the d-band with increasing pressure. en-copyright= kn-copyright= en-aut-name=EzenwaInnocent C. en-aut-sei=Ezenwa en-aut-mei=Innocent C. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= en-keyword=electrical resistivity kn-keyword=electrical resistivity en-keyword=thermal conductivity kn-keyword=thermal conductivity en-keyword=electrons and phonons interactions kn-keyword=electrons and phonons interactions en-keyword=high pressure and temperature kn-keyword=high pressure and temperature en-keyword=constant resistivity kn-keyword=constant resistivity en-keyword=melting curve kn-keyword=melting curve END start-ver=1.4 cd-journal=joma no-vol=8 cd-vols= no-issue=13 article-no= start-page=eabm1821 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2022 dt-pub=20220330 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Viscosity of bridgmanite determined by in situ stress and strain measurements in uniaxial deformation experiments en-subtitle= kn-subtitle= en-abstract= kn-abstract=To understand mantle dynamics, it is important to determine the rheological properties of bridgmanite, the dominant mineral in Earthfs mantle. Nevertheless, experimental data on the viscosity of bridgmanite are quite limited due to experimental difficulties. Here, we report viscosity and deformation mechanism maps of bridgmanite at the uppermost lower mantle conditions obtained through in situ stress-strain measurements of bridgmanite using deformation apparatuses with the Kawai-type cell. Bridgmanite would be the hardest among mantle constituent minerals even under nominally dry conditions in the dislocation creep region, consistent with the observation that the lower mantle is the hardest layer. Deformation mechanism maps of bridgmanite indicate that grain size of bridgmanite and stress conditions at top of the lower mantle would be several millimeters and ~105 Pa to realize viscosity of 1021?22 Pa?s, respectively. This grain size of bridgmanite suggests that the main part of the lower mantle is isolated from the convecting mantle as primordial reservoirs. en-copyright= kn-copyright= en-aut-name=TsujinoNoriyoshi en-aut-sei=Tsujino en-aut-mei=Noriyoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YamazakiDaisuke en-aut-sei=Yamazaki en-aut-mei=Daisuke kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=NishiharaYu en-aut-sei=Nishihara en-aut-mei=Yu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=HigoYuji en-aut-sei=Higo en-aut-mei=Yuji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=TangeYoshinori en-aut-sei=Tange en-aut-mei=Yoshinori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=Geodynamics Research Center, Ehime University kn-affil= affil-num=4 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=5 en-affil=Japan Synchrotron Radiation Research Institute kn-affil= affil-num=6 en-affil=Japan Synchrotron Radiation Research Institute kn-affil= END start-ver=1.4 cd-journal=joma no-vol= cd-vols= no-issue= article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2024 dt-pub=20240310 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Wetting property of Fe]S melt in solid core: Implication for the core crystallization process in planetesimals en-subtitle= kn-subtitle= en-abstract= kn-abstract=In differentiated planetesimals, the liquid core starts to crystallize during secular cooling, followed by the separation of liquid?solid phases in the core. The wetting property between liquid and solid iron alloys determines whether the core melts are trapped in the solid core or they can separate from the solid core during core crystallization. In this study, we performed high-pressure experiments under the conditions of the interior of small bodies (0.5?3.0?GPa) to study the wetting property (dihedral angle) between solid Fe and liquid Fe-S as a function of pressure and duration. The measured dihedral angles are approximately constant after 2?h and decrease with increasing pressure. The dihedral angles range from 30‹ to 48‹, which are below the percolation threshold of 60‹ at 0.5?3.0?GPa. The oxygen content in the melt decreases with increasing pressure and there are strong positive correlations between the S?+?O or O content and the dihedral angle. Therefore, the change in the dihedral angle is likely controlled by the O content of the Fe-S melt, and the dihedral angle tends to decrease with decreasing O content in the Fe-S melt. Consequently, the Fe-S melt can form interconnected networks in the solid core. In the obtained range of the dihedral angle, a certain amount of the Fe-S melt can stably coexist with solid Fe, which would correspond to the gtrapped melth in iron meteorites. Excess amounts of the melt would migrate from the solid core over a long period of core crystallization in planetesimals. en-copyright= kn-copyright= en-aut-name=MatsubaraShiori en-aut-sei=Matsubara en-aut-mei=Shiori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TerasakiHidenori en-aut-sei=Terasaki en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=UrakawaSatoru en-aut-sei=Urakawa en-aut-mei=Satoru kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=YumitoriDaisuke en-aut-sei=Yumitori en-aut-mei=Daisuke kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil=Department of Earth Sciences, Graduate School of Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Department of Earth Sciences, Graduate School of Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=4 en-affil=Department of Earth Sciences, Graduate School of Science and Technology, Okayama University kn-affil= affil-num=5 en-affil=Department of Earth Sciences, Graduate School of Science and Technology, Okayama University kn-affil= END