Hydroxyl group/fluorine disorder in deuterated magnesium hydroxyfluoride and behaviors of hydrogen bonds under high pressure

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

https://doi.org/10.1016/j.molstruc.2024.138271

High-pressure responses of the O-DF 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.

Behavior of light elements in iron-silicate-water-sulfur system during early Earth's evolution

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

https://doi.org/10.1038/s41598-021-91801-3

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.

Crystal and magnetic structures of double hexagonal close-packed iron deuteride

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

https://doi.org/10.1038/s41598-020-66669-4

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.

Hydrogenation of iron in the early stage of Earth's evolution

Iizuka, Riko*; Yagi, Takehiko*; Goto, Hirotada*; Okuchi, Takuo*; Hattori, Takanori; Sano, Asami

Nature Communications (Internet), 8, p.14096_1 - 14096_7, 2017/01

AA2016-0524.pdf:0.73MB

https://doi.org/10.1038/ncomms14096

Density of the Earth's core is lower than that of pure iron and the light element(s) in the core is a long-standing problem. Hydrogen is the most abundant element in the solar system and thus one of the important candidates. However, the dissolution process of hydrogen into iron remained unclear. Here we carry out high-pressure and high-temperature in situ neutron diffraction experiments and clarify that when the mixture of iron and hydrous minerals are heated, iron is hydrogenized soon after the hydrous mineral is dehydrated. This implies that early in the Earth's evolution, as the accumulated primordial material became hotter, the dissolution of hydrogen into iron occurred before any other materials melted. This suggests that hydrogen is likely the first light element dissolved into iron during the Earth's evolution and it may affect the behaviour of the other light elements in the later processes.

Phase transitions and hydrogen bonding in deuterated calcium hydroxide; High-pressure and high-temperature neutron diffraction measurements

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

https://doi.org/10.1016/j.jssc.2014.06.010

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.

Pressure responses of portlandite and H-D isotope effects on pressure-induced phase transitions

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

https://doi.org/10.1007/s00269-011-0450-3

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.

In situ neutron diffraction measurement on deuterization process of iron at high pressure and high temperature

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.

Structural studies of iron deuteride by in-situ neutron diffraction measurements under high temperature and high pressure

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

A Neutron diffraction study of phase transition in lawsonite at high pressure

Sano, Asami; Nagai, Takaya*; Iizuka, Riko*; Seto, Yusuke*; Kuribayashi, Takahiro*; Hattori, Takanori

no journal, , 

Lawsonite is a hydrous mineral which is considered as a main carrier of hydrogen in the subtucting slab. Previous single crystal X-ray diffraction and neutron diffraction studies indicate that there exist two phase transitions at low temperature. A property of low temperature is sometimes considered to be equivalent to the behavior at high pressure, and some studies pointed out the possibility of transition at high pressure. To investigate the pressure response of hydrogen bond and phase transition in lawsonite, neutron diffraction experiment was conducted. High pressure and high temperature neutron diffraction experiment was conducted by 6-ram press at J-PARC MLF. Using 6-6 type anvil with TEL size of 10 mm, neutron diffraction pattern was corrected up to 6 GPa and 800C. In addition, hydrostatic experiment at ambient pressure was conducted using Paris-Edinburgh press. New peak was observed at 1.83 that indicates phase transition at high pressure.

A Study on effects and influence of -irradiation to foodstuffs of the Japanese-style dishes

Chiba, Etsuko*; Iizuka, Tomoko*; Ichikawa, Mariko*; Ukai, Mitsuko*; Kikuchi, Masahiro; Kobayashi, Yasuhiko

no journal, , 

no abstracts in English