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He, X.*; Kagi, Hiroyuki*; Komatsu, Kazuki*; Iizuka, Riko*; Okajima, Hajime*; Hattori, Takanori; Sano, Asami; Machida, Shinichi*; Abe, Jun*; Goto, Hirotada*; et al.
Journal of Molecular Structure, 1310, p.138271_1 - 138271_8, 2024/08
High-pressure responses of the O-D
F hydrogen bonds in deuterated magnesium hydroxyfluoride were investigated using neutron powder diffraction and Raman spectroscopy. The Rietveld analysis at ambient conditions revealed a chemical formula of Mg(OD)
F
and hydroxyl group/fluorine disorder (OD/F disorder) in the crystal structure, which gave rise to two hydrogen-bonding configurations. The Rietveld analysis showed the hydrogen-bonding geometries remains up to 9.8 GPa, indicating no pressure-induced strengthening of hydrogen bonds. The Raman spectra at ambient conditions showed three hydroxyl stretching bands at 2613, 2694, and 2718 cm
. The high frequencies of the O-D stretching modes indicated that the hydroxyls should be involved in weak or none hydrogen-bonding interactions. Up to 20.2 GPa, the mode initially centered at 2694 cm displayed a pressure-induced blue shift, revealing no strengthening of hydrogen bonds under compression. We discuss the existence of hydrogen bonds and the causes of the blue-shifting hydroxyls at ambient and at high pressures.
Ni
D
at high 
conditionsShito, Chikara*; Kagi, Hiroyuki*; Kakizawa, Sho*; Aoki, Katsutoshi*; Komatsu, Kazuki*; Iizuka, Riko*; Abe, Jun*; Saito, Hiroyuki*; Sano, Asami; Hattori, Takanori
American Mineralogist, 108(4), p.659 - 666, 2023/04
Times Cited Count：1 Percentile：59.64(Geochemistry & Geophysics)The phase relation and crystal structure of FeNiH (D) at high pressures and temperatures up to 12 GPa and 1000 K were clarified by in-situ X-ray and neutron diffraction measurements. Under conditions of the present study, no deuterium atoms occupied tetragonal (
) sites of face-centered cubic (fcc) FeNiD unlike fcc FeH(D). The deuterium-induced volume expansion per deuterium 
was determined as 2.45(4) 
and 3.31(6) for fcc and hcp phases, respectively, which were significantly larger than the corresponding values for FeD. The value slightly increased with increasing temperature. This study suggests that only 10% of nickel in iron drastically changes the behaviors of hydrogen in metal. Assuming that is constant regardless of pressure, the maximum hydrogen content in the Earth's inner core is estimated to be one to two times the amount of hydrogen in the oceans.
Iizuka, Riko*; Goto, Hirotada*; Shito, Chikara*; Fukuyama, Ko*; Mori, Yuichiro*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Kagi, Hiroyuki*
Scientific Reports (Internet), 11(1), p.12632_1 - 12632_10, 2021/06
Times Cited Count：3 Percentile：30.98(Multidisciplinary Sciences)The Earth's core consist of Fe-Ni alloy with some light elements (H, C, O, Si, S etc.). Hydrogen (H) is the most abundant element in the universe and one of the promising candidates. In this study, we have investigated the effects of sulfur(S) on hydrogenation of iron-hydrous silicate system containing saturated water in the ideal composition of the primitive Earth. We observed a series of phase transitions of Fe, dehydration of the hydrous mineral, and formation of olivine and enstatite with increasing temperature. The FeS formed as the coexisting phase of Fe under high-pressure and temperature condition, but its unit cell volume did not increase, suggesting that FeS is hardly hydrogenated. Recovered samples exhibited that H and S can be incorporated into solid Fe, which lowers the melting temperature as Fe(H
)-FeS system. No detection of other light elements (C, O, Si) in solid Fe suggests that they dissolve into molten iron hydride and/or FeS in the later process of Earth's core-mantle differentiation.
Si
at 14.7 GPa and 800 KMori, Yuichiro*; Kagi, Hiroyuki*; Kakizawa, Sho*; Komatsu, Kazuki*; Shito, Chikara*; Iizuka, Riko*; Aoki, Katsutoshi*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; et al.
Journal of Mineralogical and Petrological Sciences, 116(6), p.309 - 313, 2021/00
Times Cited Count：0 Percentile：0.02(Mineralogy)The Earth's core is believed to contain some light elements because it is 10% less dense than pure Fe under the corresponding pressure and temperature conditions. Hydrogen, a promising candidate among light elements, has phase relations and physical properties that have been investigated mainly for the Fe-H system. This study specifically examined an Fe-Si-H system using in-situ neutron diffraction experiments to investigate the site occupancy of deuterium of hcp-FezSi hydride at 14.7 GPa and 800 K. Results of Rietveld refinement indicate hcp-FeSi hydride as having deuterium (D) occupancy of 0.24(2) exclusively at the interstitial octahedral site in the hcp lattice. The effect on the site occupancy of D by addition of 2.6 wt% Si into Fe (FeSi) was negligible compared to results obtained from an earlier study of an Fe-D system (Machida et al., 2019).
Saito, Hiroyuki*; Machida, Akihiko*; Iizuka, Riko*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Sato, Toyoto*; Orimo, Shinichi*; Aoki, Katsutoshi*
Scientific Reports (Internet), 10, p.9934_1 - 9934_8, 2020/06
Times Cited Count：3 Percentile：14.67(Multidisciplinary Sciences)Neutron powder diffraction profiles were collected for iron deuteride (FeDx) while the temperature decreased from 1023 to 300 K for a pressure range of 4-6 GPa. The 
' deuteride with a double hexagonal close-packed (dhcp) structure, which coexisted with other stable or metastable deutrides at each temperature and pressure condition, formed solid solutions with a composition of FeD
at 673 K and 6.1 GPa and FeD
at 603 K and 4.8 GPa. Upon stepwise cooling to 300 K, the D-content x increased to a stoichiometric value of 1.0 to form monodeuteride FeD
. In the dhcp FeD at 300 K and 4.2 GPa, dissolved D atoms fully occupied the octahedral interstitial sites, slightly displaced from the octahedral centers in the dhcp metal lattice, and the dhcp sequence of close-packed Fe planes contained hcp-stacking faults at 12%. Magnetic moments with 2.11 
0.06 B/Fe-atom aligned ferromagnetically in parallel on the Fe planes.
Iizuka, Riko*; Komatsu, Kazuki*; Kagi, Hiroyuki*; Nagai, Takaya*; Sano, Asami; Hattori, Takanori; Goto, Hirotada*; Yagi, Takehiko*
Journal of Solid State Chemistry, 218, p.95 - 102, 2014/10
Times Cited Count：7 Percentile：33.69(Chemistry, Inorganic & Nuclear)In situ neutron diffraction measurements combined with the pulsed neutron source at the Japan Proton Accelerator Research Complex (J-PARC) were conducted on high-pressure polymorphs of deuterated portlandite (Ca(OD)
) using a Paris-Edinburgh cell and a multi-anvil press. The atomic positions including hydrogen for the unquenchable high-pressure phase at room temperature (phase II') were first clarified. The bent hydrogen bonds under high pressure were consistent with results from Raman spectroscopy. The structure of the high-pressure and high-temperature phase (Phase II) was concordant with that observed previously by another group for a recovered sample. The observations elucidate the phase transition mechanism among the polymorphs, which involves the sliding of CaO polyhedral layers, position modulations of Ca atoms, and recombination of Ca-O bonds accompanied by the reorientation of hydrogen to form more stable hydrogen bonds.
Machida, Akihiko; Saito, Hiroyuki; Sugimoto, Hidehiko*; Hattori, Takanori; Sano, Asami; Endo, Naruki*; Katayama, Yoshinori; Iizuka, Riko*; Sato, Toyoto*; Matsuo, Motoaki*; et al.
Nature Communications (Internet), 5, p.5063_1 - 5063_6, 2014/09
Times Cited Count：55 Percentile：86.07(Multidisciplinary Sciences)Iron hydride FeH, is thermodynamically stable only at high hydrogen pressure of several GPa. To investigate the hydrogenation process and hydrogen state in iron hydride, it is necessary to carry out the in-situ measurement under high pressure and high temperature. In this study, we performed the in-situ neutron diffraction measurement of Fe-D system using the high pressure neutron diffractometer PLANET in the MLF, J-PARC, and determined the deuterium occupying sites and occupancies in fcc-FeD. We found the minor occupation of tetrahedral sites under high pressure and high temperature. We considered the mechanism of the minor occupation based on the Quantum-mechanical calculation.
Iizuka, Riko*; Kagi, Hiroyuki*; Komatsu, Kazuki*; Ushijima, Daichi*; Nakano, Satoshi*; Sano, Asami; Nagai, Takaya*; Yagi, Takehiko*
Physics and Chemistry of Minerals, 38(10), p.777 - 785, 2011/12
Times Cited Count：10 Percentile：33.24(Materials Science, Multidisciplinary)The pressure responses of portlandite and the isotope effect on the phase transition were investigated at room temperature from single-crystal Raman and IR spectra and from powder X-ray diffraction using diamond anvil cells under quasi-hydrostatic conditions in a helium pressure-transmitting medium. Phase transformation and subsequent peak broadening observed from the Raman and IR spectra of Ca(OH) occurred at lower pressures than those of Ca(OD). In contrast, no isotope effect was found on the volume and axial compressions observed from powder X-ray diffraction patterns. X-ray diffraction lines attributable to the high-pressure phase remained up to 28.5 GPa, suggesting no total amorphization in a helium pressure medium within the examined pressure region. These results suggest that the H-D isotope effect is engendered in the local environment surrounding H(D) atoms.
Fumizawa, Motoo; Iizuka, Hiroyuki*
Kashika Joho Gakkai-Shi, 17(SUPPL.1), p.285 - 288, 1997/07
no abstracts in English
Arakawa, Masashi*; Komatsu, Kazuki*; Iizuka, Riko*; Kagi, Hiroyuki; Fernandez-Baca, J. A.*; Chakoumakos, B.*; Yamauchi, Hiroki; Fukazawa, Hiroshi
no journal, ,
We prepared ice XI from different kinds of alkali metal hydroxide solutions with different concentrations, and measured neutron powder diffraction at JRR-3 (Japan Atomic Energy Agency, Japan) and HFIR (Oak Ridge National Laboratory, TN, USA). Rietveld analysis was carried out for the obtained diffraction patterns using a two-phase model, which includes ices Ih and XI. The hydrogen-ordered structure in the lithium-doped ice was the same as that in the sodium-doped and potassium-doped ices. We also confirmed the optimum formation condition of ice XI for the temperature history and concentration of solution. Furthermore, our results indicate that the phase transition from ice Ih to XI occurs in the doped ice that had once been ice XI to a notably larger degree than in the doped ice that had never transformed to ice XI. We named this phenomenon memory effect of hydrogen ordering.
Abe, Jun; Hattori, Takanori; Arima, Hiroshi; Sano, Asami; Fukazawa, Hiroshi; Utsumi, Wataru; Komatsu, Kazuki*; Arakawa, Masashi*; Iizuka, Riko*; Kagi, Hiroyuki*; et al.
no journal, ,
In order to confirm the feasibility of high-pressure neutron diffraction at TAKUMI, we have performed a number of R&Ds using a various high-pressure devices. Optimization of materials such as anvil and pressure medium and developments of collimators have made possible reduction of background and contamination noise. Incident and diffracted neutron beams travel through high-pressure device, which causes attenuation of neutron. We investigated the method of attenuation correction.
Ichikawa, Mariko*; Iizuka, Tomoko*; Chiba, Etsuko*; Okamura, Hiroyuki*; Tabei, Yutaka*; Morita, Maki*; Yokoyama, Tsutomu*; Fukutomi, Fumitake*; Sakagami, Chiharu*; Ukai, Mitsuko*; et al.
no journal, ,
no abstracts in English
Abe, Jun; Arima, Hiroshi; Hattori, Takanori; Sano, Asami; Fukazawa, Hiroshi; Utsumi, Wataru; Komatsu, Kazuki*; Arakawa, Masashi*; Iizuka, Riko*; Kagi, Hiroyuki; et al.
no journal, ,
We have performed high-pressure neutron diffraction experiments at TAKUMI in J-PARC. Three types of high-pressure devices are used, Paris-Edinburgh Press, Palm cubic anvil cell and NPD-DAC. Optimization of materials such as anvil and pressure medium and developments of collimators have made possible reduction of background and contamination noise. Incident and diffracted neutron beams travel through high-pressure device, which causes attenuation of neutron. We have studied the method of attenuation correction and analyzed crystal structure using corrected neutron diffraction pattern.
Machida, Akihiko; Saito, Hiroyuki; Hattori, Takanori; Sano, Asami; Endo, Naruki; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Sato, Toyoto*; Matsuo, Motoaki*; et al.
no journal, ,
no abstracts in English
Machida, Akihiko; Saito, Hiroyuki; Hattori, Takanori; Sano, Asami; Endo, Naruki*; Watanuki, Tetsu; Katayama, Yoshinori; Iizuka, Riko*; Sato, Toyoto*; Matsuo, Motoaki*; et al.
no journal, ,
Iron hydride FeH, is thermodynamically stable only at high hydrogen pressure of several GPa. Three hydride phases, bcc-FeH (
), dhcp-FeH (
), and fcc-FeH (
) were confirmed at 300-2000 K and 0-20 GPa. In situ neutron diffraction measurement on their deutrides have not been reported yet. A high pressure neutron diffractometor, PLANET, constructed at Materials and Life Science Experimental Facility at J-PARC, enables us to perform in situ neutoron diffraction measurements on deuterization process of metals at high pressure and high temperature. With PLANET, the deuteration process of iron was investigated at a pressure of about 7 GPa and temperatures up to about 1000 K. This in situ measurement was successfully made using a deuterization reaction cell developed for neutron diffraction measurement. We observed the bcc-fcc transition of pure iron around 800 K and successive deuterization of fcc-Fe around 870 K.
neutron diffraction measurement on the deuterization process of Fe at high temperature and high pressureMachida, Akihiko; Saito, Hiroyuki; Hattori, Takanori; Sano, Asami; Endo, Naruki; Watanuki, Tetsu; Katayama, Yoshinori; Iizuka, Riko*; Sato, Toyoto*; Matsuo, Motoaki*; et al.
no journal, ,
no abstracts in English
Machida, Akihiko; Saito, Hiroyuki; Hattori, Takanori; Sano, Asami; Endo, Naruki; Watanuki, Tetsu; Katayama, Yoshinori; Iizuka, Riko*; Sato, Toyoto*; Matsuo, Motoaki*; et al.
no journal, ,
no abstracts in English
