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Journal Articles

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-D$$cdotcdotcdot$$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)$$_{0.920(12)}$$F$$_{1.080(12)}$$ 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$$^{-1}$$. 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$$^{-1}$$ 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.

Journal Articles

Hydrogenation of silicon-bearing hexagonal close-packed iron and its implications for density deficits in the inner core

Mori, Yuichiro*; Kagi, Hiroyuki*; Aoki, Katsutoshi*; Takano, Masahiro*; Kakizawa, Sho*; Sano, Asami; Funakoshi, Kenichi*

Earth and Planetary Science Letters, 634, p.118673_1 - 118673_8, 2024/05

https://doi.org/10.1016/j.epsl.2024.118673

To investigate silicon effects on the hydrogen-induced volume expansion of iron, neutron diffraction and X-ray diffraction experiments were conducted to examine hcp-Fe$$_{0.95}$$Si$$_{0.05}$$ under high pressures and high temperatures. Neutron diffraction experiments were performed on the deuterated hcp-Fe$$_{0.95}$$Si$$_{0.05}$$ at 13.5 GPa and 900 K, and at 12.1 GPa and 300 K. By combining the P-V-T equation of state of hcp-Fe$$_{0.95}$$Si$$_{0.05}$$, present results indicate that the hydrogen-induced volume expansion of hcp-Fe$$_{0.95}$$Si$$_{0.05}$$ is 10% greater than that of pure hcp iron. Using the obtained values, we estimated the hydrogen content that would reproduce the density deficit in the inner core, which was 50% less than that without the effect of silicon. Possible hydrogen content, $$x$$, in the inner core and the outer core was calculated to be 0.07 and 0.12-0.15, respectively, when reproducing the density deficit of the inner core with hcp-Fe$$_{0.95}$$Si$$_{0.05}$$Hx.

Journal Articles

Development of 0.5 mm gauge size radial collimators for high-pressure neutron diffraction experiments at PLANET in J-PARC

Hattori, Takanori; Suzuki, Koji*; Miyo, Tatsuya*; Ito, Takayoshi*; Machida, Shinichi*

Nuclear Instruments and Methods in Physics Research A, 1059, p.168956_1 - 168956_9, 2024/02

https://doi.org/10.1016/j.nima.2023.168956
 Times Cited Count：0 Percentile：0.02(Instruments & Instrumentation)

Radial collimators (RC) with a 0.5 mm gauge size (GS) were specially designed for high-pressure neutron diffraction experiments and their performance and efficacy were investigated. The RCs with nominal GS of 0.75 mm, 1.5 mm, and 3.0 mm effectively exhibited GS of 0.50 mm, 1.07 mm, and 2.78 mm, respectively. The transmissions of all three RCs were almost equivalent. The assessment using a P-E press and a DAC revealed that the anvil scattering was considerably minimized and the sample-to-anvil signal ratio reached values of 0.5 and 2.0 for the PE press and DAC, respectively, when using the 0.5 mm-GS RCs. These results indicate that the 0.5mm-GS RCs have been fabricated as intended and exhibit efficacy for the high-pressure-neutron diffraction experiments, specifically those exceeding 30 GPa. Among those ever manufactured for neutron scattering experiments, the RCs display the smallest GS.

Journal Articles

Slightly hydrogen-ordered state of ice IV evidenced by ${it in situ}$ neutron diffraction

Kobayashi, Hiroki*; Komatsu, Kazuki*; Ito, Hayate*; Machida, Shinichi*; Hattori, Takanori; Kagi, Hiroyuki*

Journal of Physical Chemistry Letters (Internet), 14(47), p.10664 - 10669, 2023/11

https://doi.org/10.1021/acs.jpclett.3c02563
 Times Cited Count：0 Percentile：0.01(Chemistry, Physical)

Ice IV is a metastable high-pressure phase of ice in which the water molecules exhibit orientational disorder. Although orientational ordering is commonly observed for other ice phases, it has not been reported for ice IV. We conducted ${it in situ}$ powder neutron diffraction experiments for DCl-doped D$$_{2}$$O ice IV to investigate hydrogen ordering in ice IV. We found abrupt changes in the temperature derivative of unit cell volume, dV/dT, at about 120 K, and revealed their slightly ordered structure at low temperatures based on the Rietveld method. The occupancy of the D1 site deviates from 0.5; it increased when samples were cooled at higher pressures and reached 0.282(5) at 2.38 GPa, 58 K. Our results evidence the presence of a low-symmetry hydrogen-ordered state corresponding to ice IV. It seems, however, difficult to experimentally access the completely ordered phase corresponding to ice IV by slow cooling at high pressure.

Journal Articles

The Hydrogen-bond network in sodium chloride tridecahydrate; Analogy with ice VI

Yamashita, Keishiro*; Nakayama, Kazuya*; Komatsu, Kazuki*; Ohara, Takashi; Munakata, Koji*; Hattori, Takanori; Sano, Asami; Kagi, Hiroyuki*

Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 79(5), p.414 - 426, 2023/10

https://doi.org/10.1107/S2052520623007199
 Times Cited Count：0 Percentile：0.02(Chemistry, Multidisciplinary)

The structure of a recently-found hyperhydrated form of sodium chloride, NaCl$$cdot$$ 13H(D)$$_{2}$$O, has been determined by ${it in situ}$ single-crystal neutron diffraction at 1.7 GPa and 298 K. It has large hydrogen-bond networks and some water molecules have distorted bonding features such as bifurcated hydrogen bonds and five-coordinated water molecules. The hydrogen-bond network has similarities to ice VI in terms of network topology and disordered hydrogen bonds. Assuming the equivalence of network components connected by pseudo symmetries, the overall network structure of this hydrate can be expressed by breaking it down into smaller structural units which correspond to the ice VI network structure. This hydrogen-bond network contains orientational disorder of water molecules in contrast to the known salt hydrates. Here, we present an example for further insights into a hydrogen-bond network containing ionic species.

Journal Articles

Deuterium content and site occupancy in iron sulfide at high pressure and temperature determined using in situ neutron diffraction measurements

Abeykoon, S.*; Howard, C.*; Dominijanni, S.*; Eberhard, L.*; Kurnosov, A.*; Frost, D. J.*; Boffa Ballaran, T.*; Terasaki, Hidenori*; Sakamaki, Tatsuya*; Suzuki, Akio*; et al.

Journal of Geophysical Research; Solid Earth, 128(9), p.e2023JB026710_1 - e2023JB026710_17, 2023/09

https://doi.org/10.1029/2023JB026710
 Times Cited Count：0 Percentile：0.01(Geochemistry & Geophysics)

Small amounts of iron sulphide minerals are found in most rocks from the Earth's mantle and as inclusions trapped in natural diamonds. Hydrogen may dissolve into iron sulphide minerals under high pressures and temperature, but is most likely lost once pressure and temperature are removed. In this study, we determined deuterium contents in iron sulphide, held under high pressure and temperature conditions, using neutron diffraction measurements with 6-ram multi-anvil press at PLANET, J-PARC. Deuterium contents in iron sulphide were measured at high-P, up to 11.4 GPa and high-T to 1300 K in in situ neutron diffraction experiments. The total deuterium content increases with both P and T. The results are used to estimate hydrogen contents of iron sulphide minerals in the deep continental lithospheric mantle, which are found to be in the range 1700-2700 ppm. This corresponds to approximately 2-3 ppm of hydrogen in the bulk mantle.

Journal Articles

Hydrogen occupation and hydrogen-induced volume expansion in Fe$$_{0.9}$$Ni$$_{0.1}$$D$$_x$$ at high $$P-T$$ conditions

Shito, 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

https://doi.org/10.2138/am-2022-8348
 Times Cited Count：1 Percentile：64.83(Geochemistry & Geophysics)

The phase relation and crystal structure of Fe$$_{0.9}$$Ni$$_{0.1}$$H$$_x$$ (D$$_x$$) at high pressures and temperatures up to 12 GPa and 1000 K were clarified by in-situ X-ray and neutron diffraction measurements. Under $$P-T$$ conditions of the present study, no deuterium atoms occupied tetragonal ($$T$$) sites of face-centered cubic (fcc) Fe$$_{0.9}$$Ni$$_{0.1}$$D$$_x$$ unlike fcc FeH$$_x$$(D$$_x$$). The deuterium-induced volume expansion per deuterium $$v_mathrm{D}$$ was determined as 2.45(4) $AA$^3$$ and 3.31(6) $AA$^3$$ for fcc and hcp phases, respectively, which were significantly larger than the corresponding values for FeD$$_x$$. The $$v_mathrm{D}$$ 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 $$v_mathrm{D}$$ 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.

Journal Articles

Neutron scattering on an aqueous sodium chloride solution in the gigapascal pressure range

Yamaguchi, Toshio*; Yoshida, Koji*; Machida, Shinichi*; Hattori, Takanori

Journal of Molecular Liquids, 365, p.120181_1 - 120181_10, 2022/11

https://doi.org/10.1016/j.molliq.2022.120181
 Times Cited Count：1 Percentile：16.81(Chemistry, Physical)

Neutron scattering measurements were performed on an aqueous 3 mol/kg NaCl solution in D$$_2$$O at temperature and pressure conditions of 0.1 MPa/298K, 1 GPa/298K, 1 GPa/523K, and 4 GPa/523K. The empirical potential structure refinement method was applied to the obtained data to extract the pair correlation function, coordination number distribution, angular distribution (orientation correlation), and spatial density function (3-D structure). From those results, pressure and temperature dependence of solvation and association of ions and solvent-water structure were discussed.

Journal Articles

Hydrogen vibration excitations of ZrH$$_{1.8}$$ and TiH$$_{1.84}$$ up to 21 GPa by incoherent inelastic neutron scattering

Hattori, Takanori; Nakamura, Mitsutaka; Iida, Kazuki*; Machida, Akihiko*; Sano, Asami; Machida, Shinichi*; Arima, Hiroshi*; Oshita, Hidetoshi*; Honda, Takashi*; Ikeda, Kazutaka*; et al.

Physical Review B, 106(13), p.134309_1 - 134309_9, 2022/10

https://doi.org/10.1103/PhysRevB.106.134309
 Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)

Hydrogen vibration excitations of fluorite-type ZrH$$_{1.8}$$ and TiH$$_{1.84}$$ were investigated up to 21 GPa and 4 GPa, respectively, by incoherent inelastic neutron scattering experiments. The first excitation energies increased with pressure, as described by the equations $$E_1$$(meV) = 141.4(2) + 1.02(2)$$P$$(GPa) and $$E_1$$(meV) = 149.4(1) + 1.21(8)$$P$$(GPa) for ZrH$$_{1.8}$$ and TiH$$_{1.84}$$, respectively. Coupling with pressure dependence of lattice parameters, the relations between metal-hydrogen distance ($$d_{M-H}$$) and $$E_1$$ are found to be well described by the equations $$E_1$$(meV) = 1.62(9)$$times$$ 10$$^3$$ $$d_{M-H}^{-3.31(8)}$$($AA) and $E_1$$(meV) = 1.47(21)$$times$$ 10$$^3$$ $$d_{M-H}^{-3.5(2)}$$(AA), respectively. The slopes of these curves are much steep compared to the previously reported trend in various fluorite-type metal hydrides at ambient pressure. The hydrogen wave function spreading showed that the local potential field for a hydrogen atom shrinks more intensively than the tetrahedral site. These behavior is likely caused by the rigid metal ion core and the resulting confinement of the hydrogen atom in the narrower potential field at high pressures.

Journal Articles

Magnetic and structure transition of Mn$$_{3-x}$$Fe$$_x$$O$$_4$$ solid solutions under high-pressure and high-temperature conditions

Yamanaka, Takamitsu*; Hirao, Naohisa*; Nakamoto, Yuki*; Mikouchi, Takashi*; Hattori, Takanori; Komatsu, Kazuki*; Mao, H.-K.*

Physics and Chemistry of Minerals, 49(10), p.41_1 - 41_14, 2022/10

https://doi.org/10.1007/s00269-022-01215-4
 Times Cited Count：0 Percentile：0.02(Materials Science, Multidisciplinary)

Magnetic and crystal structure of Mn$$_{3-x}$$Fe$$_x$$O$$_4$$ solid solutions under high-PT conditions are investigated by neutron diffraction and synchrotron M${"o}$ssbauer spectroscopy. The ferrimagnetic-paramagnetic transition and tetragonal-cubic transition of Mn$$_2$$FeO$$_4$$ spinel occur at 100$$^circ$$C and 180$$^circ$$C, respectively, suggesting both the transitions are not coupled. The structure transition temperature decreases with pressure. M${"o}$ssbauer experiments and neutron diffraction revealed that the Fe$$^{2+}$$ occupancy in tetrahedral site increases increase with pressure, suggesting Mn$$_2$$FeO$$_4$$ phase approaches inverse spinel. Magnetic structure refinement clarified paramagnetic and ferrimagnetic structure of MnFe$$_2$$O$$_4$$ and Mn$$_2$$FeO$$_4$$. These spinels transform into high-pressure orthorhombic phases at 18.4 and 14.0 GPa, respectively, indicating lower transition pressure with increasing Mn content.

Journal Articles

Atomic distribution and local structure in ice VII from in situ neutron diffraction

Yamashita, Keishiro*; Komatsu, Kazuki*; Klotz, S.*; Fabelo, O.*; Fern$'a$ndez-D$'i$az, M. T.*; Abe, Jun*; Machida, Shinichi*; Hattori, Takanori; Irifune, Tetsuo*; Shimmei, Toru*; et al.

Proceedings of the National Academy of Sciences of the United States of America, 119(40), p.e2208717119_1 - e2208717119_6, 2022/10

https://doi.org/10.1073/pnas.2208717119
 Times Cited Count：2 Percentile：22.35(Multidisciplinary Sciences)

Here we present the first elucidation of the disordered structure of ice VII, the dominant high-pressure form of water, at 2.2 GPa and 298 K from both single-crystal and powder neutron diffraction techniques. We reveal the three-dimensional atomic distributions from the maximum entropy method and unexpectedly find a ring-like distribution of hydrogen in contrast to the commonly-accepted discrete sites. In addition, total scattering analysis at 274 K clarified the difference in the intermolecular structure from ice VIII, the ordered counterpart of ice VII, despite an identical molecular geometry. Our complementary structure analyses robustly demonstrate the unique disordered structure of ice VII. Furthermore, these noble findings are related to the proton dynamics which drastically vary with pressure, and will contribute to an understanding of the structural origin of anomalous physical properties of ice VII under pressures.

Journal Articles

Enhancement of electrical conductivity to metallization of Mn$$_{3-x}$$Fe$$_x$$O$$_4$$ spinel and postspinel with elevating pressure

Yamanaka, Takamitsu*; Rahman, S.*; Nakamoto, Yuki*; Hattori, Takanori; Jang, B. G.*; Kim, D. Y.*; Mao, H.-K.*

Journal of Physics and Chemistry of Solids, 167, p.110721_1 - 110721_10, 2022/08

https://doi.org/10.1016/j.jpcs.2022.110721
 Times Cited Count：1 Percentile：15.7(Chemistry, Multidisciplinary)

High-pressure neutron diffraction proved that MnFe$$_2$$O$$_4$$ and Mn$$_2$$FeO$$_4$$ spinels transform into CaMn$$_2$$O$$_4$$-type structure above 18 GPa and 14 GPa, respectively. The transition pressure of Mn$$_{3-x}$$Fe$$_x$$O$$_4$$ solutions decreases with increasing Mn content. Synchrotron X-ray M$"{o}$ssbauer experiments revealed that Fe$$^{2+}$$ and Fe$$^{3+}$$ distribution at the tetrahedral (A) and octahedral (B) sites in the spinel structure changes with pressure. MnFe$$_2$$O$$_4$$ and Mn$$_2$$FeO$$_4$$ spinels are ferrimagnetic and the CaMn$$_2$$O$$_4$$-type phase is paramagnetic. The temperature dependence of resistivity indicates that both spinels are semiconductors wherein electrons hop between cations at the A and B sites. A pressure-induced shortening of B-B distance promoted conduction via greater electron mobility between adjacent B cations. The Fe$$^{2+}$$ and Fe$$^{3+}$$ occupancies at the B sites in MnFe$$_2$$O$$_4$$ are much larger than those in Mn$$_2$$FeO$$_4$$. The CaMn$$_2$$O$$_4$$-type phase is metallic. Theoretical calculation confirmed the metallic character and Fe d-orbitals strongly renormalized compared to Mn d-orbitals.

Journal Articles

High-pressure neutron experiments at PLANET in J-PARC using the six-axis multi-anvil press ATSUHIME

Hattori, Takanori

Yukuatsu Gijutsu, 61(7), p.29 - 35, 2022/07

As an example of the application of hydraulic technology, the 6-axis type multi-anvil press "ATSUHIME" in the J-PARC ultra-high pressure neutron diffractometer PLANET and the research on hydrogen in the Earth's core using them are introduced.

Journal Articles

Effects of potential on the electrical conductivity of a solution within a crevice of stainless steel in high-temperature water

Soma, Yasutaka; Komatsu, Atsushi; Ueno, Fumiyoshi

Corrosion, 78(6), p.503 - 515, 2022/06

https://doi.org/10.5006/3187
 Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)

The effects of electrochemical potential (ECP) on water chemistry within a crevice are of critical importance for understanding stress corrosion cracking (SCC) of Fe-Cr-Ni alloys in high temperature water. In this study, the effects of ECP on the electrical conductivity of a solution within a Type-316L stainless steel crevice ($$sigma$$$$_{crev}$$) have been studied in 288$$^{circ}$$C and 8 MPa water containing 10 ppb Cl$$^{-}$$ as major anionic species. In situ measurements of $$sigma$$$$_{crev}$$ in a rectangular crevice with a gap of 15 $$mu$$m and a depth of 23 mm have been conducted using small sensors installed at different crevice depths. An increase in ECP from -0.49 V (vs. standard hydrogen electrode) to -0.12 V resulted in an increase in $$sigma$$$$_{crev}$$ from 12 $$mu$$Scm$$^{-1}$$ to 160 $$mu$$Scm$$^{-1}$$ at a distance of 21 mm from the crevice mouth. The increase in $$sigma$$$$_{crev}$$ reached a maximum at about 0.15 V (about 300 $$mu$$Scm$$^{-1}$$) and then tended to decrease with increasing potential. Finite element model analysis taking into account the electrochemical reaction quantitatively reproduced this behavior. It is considered that Cl$$^{-}$$ is the major anionic species transported into the crevice at relatively low potentials, and that $$sigma$$$$_{crev}$$ increases monotonically with increasing ECP. On the other hand, when ECP exceeds around 0 V, a sufficient amount of HCrO$$_{4}$$$$^{-}$$ generated by transpassive dissolution also transported into the gap. Since this chemical species is highly oxidizing, unlike Cl, it is assumed that it reacts with metal cations to oxidize and precipitate them, thereby lowering conductivity.

Journal Articles

Electrochemical behavior of Fe-Cr-Ni alloys in simulated crevice condition in high temperature water

Soma, Yasutaka; Kato, Chiaki

Zairyo To Kankyo 2022 Koenshu (CD-ROM), p.219 - 220, 2022/05

It is important to understand the electrochemical properties of stainless steel in environment created within crevice of stainless steel in high temperature water (crevice environment). This is because acidification and concentration of impurity ions occur in the crevice environment and this is common inside the stress corrosion crack. In this study, we reproduced the crevice environment in bulk scale and investigated mainly the effect of Cr concentration on the electrochemical properties of Fe-Cr-Ni alloys. Polarization curves of Fe-20Ni-xCr (x=16.4, 23, 26) were measured in water with a temperature of 288$$^{circ}$$C, a Cl concentration of 2$$times$$10$$^{-4}$$ mol/dm$$^{-3}$$, a pH value of about 4.5, and a dissolved hydrogen concentration of 10 ppb. The peak currents of active dissolution (at -400 mV) and passive current density (at -50 mV) for specimens with Cr concentrations x = 16.4, 23, and 26% were approximately 13.8, 15.9, 10.0 $$mu$$Acm$$^{-2}$$, and 18.4, 8.5, 8.5 $$mu$$Acm$$^{-2}$$, respectively. Although the current values of x=26 were slightly lower in both cases, it was concluded that there was no clear dependence of the polarization curve on Cr concentration in this environment.

Journal Articles

Structure of basaltic glass at pressures up to 18 GPa

Ohashi, Tomonori*; Sakamaki, Tatsuya*; Funakoshi, Kenichi*; Hattori, Takanori; Hisano, Naoki*; Abe, Jun*; Suzuki, Akio*

American Mineralogist, 107(3), p.325 - 335, 2022/03

https://doi.org/10.2138/am-2021-7742
 Times Cited Count：1 Percentile：22.72(Geochemistry & Geophysics)

The basaltic glass structure were investigated to 18 GPa using in situ X-ray and neutron diffraction. The O-O coordination number (CN$$_textrm{OO}$$) starts to rise with maintaining the mean O-O distance (r$$_textrm{OO}$$) above 2-4 GPa, and then CN$$_textrm{OO}$$ stops increasing and r$$_textrm{OO}$$ begins to shrink along with the increase in the Al-O coordination number (CN$$_textrm{AlO}$$) above 9 GPa. This is interpreted by the change in the contraction mechanism from tetrahedral network bending to oxygen packing ratio increase via the CN$$_textrm{AlO}$$ increase. The oxygen packing fraction exceeds the value for dense random packing, suggesting that the oxygen-packing hypothesis cannot account for the pressure-induced structural transformations of silica and silicate glasses. The CN$$_textrm{OO}$$ increase at 2-4 GPa reflects the elastic softening of silicate glass, which may causes anomalous elastic moduli of basaltic glass at $$sim$$ 2 GPa.

Journal Articles

Improvement of nano-polycrystalline diamond anvil cells with Zr-based bulk metallic glass cylinder for higher pressures; Application to Laue-TOF diffractometer

Yamashita, Keishiro*; Komatsu, Kazuki*; Ohara, Takashi; Munakata, Koji*; Irifune, Tetsuo*; Shimmei, Toru*; Sugiyama, Kazumasa*; Kawamata, Toru*; Kagi, Hiroyuki*

High Pressure Research, 42(1), p.121 - 135, 2022/03

https://doi.org/10.1080/08957959.2022.2045982
 Times Cited Count：3 Percentile：58.88(Physics, Multidisciplinary)

Journal Articles

Structure of an aqueous RbCl solution in the gigapascal pressure range by neutron diffraction combined with empirical potential structure refinement modeling

Zhang, W. Q.*; Yamaguchi, Toshio*; Fang, C. H.*; Yoshida, Koji*; Zhou, Y. Q.*; Zhu, F. Y.*; Machida, Shinichi*; Hattori, Takanori; Li, W.*

Journal of Molecular Liquids, 348, p.118080_1 - 118080_11, 2022/02

https://doi.org/10.1016/j.molliq.2021.118080
 Times Cited Count：2 Percentile：34.79(Chemistry, Physical)

The ion hydration and association and hydrogen-bonded water structure in an aqueous 3 mol/kg RbCl solution were investigated at 298 K/0.1 MPa, 298 K/1 GPa, 523 K/1 GPa, and 523 K/4 GPa by neutron diffraction combined with EPSR methods. The second hydration layer of Rb$$^+$$ and Cl$$^-$$ becomes evident under elevated pressure and temperature conditions. The average oxygen coordination number of Rb$$^+$$ (Cl$$^-$$) in the first hydration layer increases from 6.3 (5.9) ambient pressure to 8.9 (9.1) at 4 GPa, while decreasing coordination distance from 0.290 nm (0.322 nm) to 0.288 nm (0.314 nm). The orientation of the water dipole in the first solvation shell of Rb$$^+$$ and a central water molecule is sensitive to pressure, but that in the first solvation shell of Cl$$^-$$ does not change very much. The number of contact-ion pairs Rb$$^+$$-Cl$$^-$$ decreases with elevated temperature and increases with elevated pressure. Water molecules are closely packed, and the tetrahedral hydrogen-bonded network of water molecules no longer exists in extreme conditions.

Journal Articles

Development of a hybrid piston cylinder cell for quasielastic neutron scattering experiments up to 1 GPa

Hattori, Takanori; Kawamura, Seiko; Kawasaki, Takuro

High Pressure Research, 42(2), p.226 - 235, 2022/00

https://doi.org/10.1080/08957959.2022.2068954
 Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)

We have developed a hybrid piston cylinder cell for quasi-elastic neutron scattering (QENS) experiments up to about 1 GPa. It consists of a fretted cylinder made of the high tensile steel (SNCM439) liner and the Al alloy (NA700) jacket. Performance tests revealed that the cell can withstand a pressure of 0.8 GPa without irreversible damage and has 4.4 times larger neutron transmission at 3.14 meV (5.10${AA}$ in wavelength) than that of a conventional CuBe monobloc cylinder. Combined with the sample assembly devised for suppressing multiple scattering, high quality QENS spectra of water were obtained up to 0.8 GPa. This study illustrates the efficacy of the hybrid cylinders not only for increasing maximum available pressure but also manipulating the available pressure and the signal intensity, depending on the purpose of the experiments.

Journal Articles

Synthesis and characterisation of a new graphitic C-S compound obtained by high pressure decomposition of CS$$_2$$

Klotz, S.*; Baptiste, B.*; Hattori, Takanori; Feng, S. M.*; Jin, Ch.*; B$'e$neut, K.*; Guigner, J. M.*; Est$`e$ve, I.*

Carbon, 185, p.491 - 500, 2021/11

https://doi.org/10.1016/j.carbon.2021.09.048
 Times Cited Count：1 Percentile：6.33(Chemistry, Physical)

Carbon disulphide (CS$$_2$$) is one of the simplest molecular systems made of double covalent bonds. Under high pressure, the molecular structure is expected to break up to form extended crystalline or polymeric solids. Here we show that by compression at 300 K to approximately $$sim$$10 GPa using large-volume high pressure techniques, an instantaneous reaction leads to a mixture of pure sulphur and a well-defined compound with stoichiometry close to C$$_2$$S which can be recovered to ambient pressure. We present neutron and X-ray diffraction as well as Raman data which show that this material consists of sulphur bonded to sp$$^2$$ graphite layers of nanometric dimensions. The compound is a semiconductor with a gap of 45 meV, as revealed by temperature dependent resistivity measurements, and annealing at temperatures above 200$$^{circ}$$C allow to reduce its sulphur content up to C$$_{10}$$S. Its structural and electronic properties are fundamentally different to "Bridgman black" reported from previous high pressure experiments on CS$$_2$$.

366 (Records 1-20 displayed on this page)