Experimental evidence for the existence of a second partially-ordered phase of ice VI

Yamane, Ryo*; Komatsu, Kazuki*; Gochi, Jun*; Uwatoko, Yoshiya*; Machida, Shinichi*; Hattori, Takanori; Ito, Hayate*; Kagi, Hiroyuki*

Nature Communications (Internet), 12, p.1129_1 - 1129_6, 2021/02

https://doi.org/10.1038/s41467-021-21351-9

Ice exhibits extraordinary structural variety in its polymorphic structures. The existence of a new form of diversity in ice polymorphism has recently been debated in both experimental and theoretical studies, questioning whether hydrogen-disordered ice can transform into multiple hydrogen-ordered phases, contrary to the known one-to-one correspondence between disordered ice and its ordered phase. Here we report a new high-pressure phase, ice XIX, which is a second hydrogen-ordered phase of ice VI. This is the first discovery to demonstrate that disordered ice undergoes different manners of hydrogen ordering. Such multiplicity can appear in all disordered ice, and it widely provides a new research approach to deepen our knowledge, for example of the crucial issues of ice: the centrosymmetry of hydrogen-ordered configurations and potentially induced (anti-)ferroelectricity. Ultimately, this research opens up the possibility of completing the phase diagram of ice.

Neutron diffraction study on the deuterium composition of nickel deuteride at high temperatures and high pressures

Saito, Hiroyuki*; Machida, Akihiko*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Sato, Toyoto*; Orimo, Shinichi*; Aoki, Katsutoshi*

Physica B; Condensed Matter, 587, p.412153_1 - 412153_6, 2020/06

https://doi.org/10.1016/j.physb.2020.412153

The site occupancy of deuterium (D) atoms in face-centered-cubic nickel (fcc Ni) was measured along a cooling path from 1073 to 300 K at an initial pressure of 3.36 GPa via in situ neutron powder diffraction. Deuterium atoms predominantly occupy the octahedral (O) sites and slightly occupy the tetrahedral (T) sites of the fcc metal lattice. The O-site occupancy increases from 0.4 to 0.85 as the temperature is lowered from 1073 to 300 K. Meanwhile, the T-site occupancy remains c.a. 0.02. The temperature-independent behavior of the T-site occupancy is unusual, and its process is not yet understood. From the linear relation between the expanded lattice volume and D content, a D-induced volume expansion of 2.09(13) atom was obtained. This value is in agreement with the values of 2.14-2.2 atom previously reported for Ni and Ni Fe alloy.

Anomalous hydrogen dynamics of the ice VII-VIII transition revealed by high-pressure neutron diffraction

Komatsu, Kazuki*; Klotz, S.*; Machida, Shinichi*; Sano, Asami; Hattori, Takanori; Kagi, Hiroyuki*

Proceedings of the National Academy of Sciences of the United States of America, 117(12), p.6356 - 6361, 2020/03

https://doi.org/10.1073/pnas.1920447117

Above 2 GPa the phase diagram of water simplifies considerably and exhibits only two solid phases up to 60 GPa, ice VII and ice VIII. The two phases are related to each other by hydrogen ordering, with the oxygen sub-lattice being essentially the same. Here we present neutron diffraction data to 15 GPa which reveal that the rate of hydrogen-ordering at the ice VII-VIII transition decreases strongly with pressure to reach time scales of minutes at 10 GPa. Surprisingly, the ordering process becomes more rapid again upon further compression. We show that such an unusual change in transition rate can be explained by a slowing-down of the rotational dynamics of water molecules with a simultaneous increase of translational motion of hydrogen under pressure, as previously suspected. The observed crossover in the hydrogen dynamics in ice is likely the origin of various hitherto unexplained anomalies of ice VII in the 10-15 GPa range reported by Raman spectroscopy, X-ray diffraction, and proton conductivity.

Crystal structure of a high-pressure phase of magnesium chloride hexahydrate determined by X-ray and neutron diffraction methods

Yamashita, Keishiro*; Komatsu, Kazuki*; Hattori, Takanori; Machida, Shinichi*; Kagi, Hiroyuki*

Acta Crystallographica Section C; Structural Chemistry (Internet), 75(12), p.1605 - 1612, 2019/12

https://doi.org/10.1107/S2053229619014670

A crystal structure of a high-pressure phase of magnesium chloride hexahydrate (MgCl 6HO-II) and its deuterated counterpart (MgCl 6DO-II) have been identified for the first time by in-situ single-crystal X-ray and powder neutron diffraction. The crystal structure was analyzed by the Rietveld method for the neutron diffraction pattern based on the initial structure determined by single-crystal X-ray diffraction. This high-pressure phase has a similar framework to that in the known ambient-pressure phase, but exhibits some structural changes with symmetry reduction caused by a subtle modification in the hydrogen-bond network around the Mg(HO) octahedra. These structural features reflect the strain in the high-pressure phases of MgCl hydrates.

Highlight of recent sample environment at J-PARC MLF

Kawamura, Seiko; Hattori, Takanori; Harjo, S.; Ikeda, Kazutaka*; Miyata, Noboru*; Miyazaki, Tsukasa*; Aoki, Hiroyuki; Watanabe, Masao; Sakaguchi, Yoshifumi*; Oku, Takayuki

Neutron News, 30(1), p.11 - 13, 2019/05

https://doi.org/10.1080/10448632.2019.1605790

In Japanese neutron scattering facilities, some SE equipment that are frequently used at an instrument, such as the closed-cycle refrigerator (CCR), have been prepared for the instrument as standard SE. They are operated for user experiments by the instrument group. The advantage of this practice is that they can optimize the design of the SE for the instrument and can directly respond to users' requests. On the other hand, the SE team in the Materials and Life Science Experimental Facility (MLF) in J-PARC has managed commonly used SE to allow neutron experiments with more advanced SE. In this report, recent SE in the MLF is introduced. Highlighted are the SE in BL11, BL19, BL21 and BL17 and other SE recently progressed by the SE team.

Occupation sites and valence states of Co dopants in (La, Co)-codoped M-type Sr ferrite; Fe and Co nuclear magnetic resonance studies

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Ueda, Hiroaki*; Tanioku, Yasuaki*; Michioka, Chishiro*; Yoshimura, Kazuyoshi*; Takao, Kenta*; Shimoda, Aiko*; et al.

Physical Review B, 98(6), p.064403_1 - 064403_10, 2018/08

https://doi.org/10.1103/PhysRevB.98.064403

To specify preferential occupation sites of Co substituents and to clarify charge and spin states of Co ions in (La, Co)-cosubstituted hexagonal magnetoplumbite-type (M-type) Sr ferrite, Fe and Co nuclear magnetic resonance (NMR) spectra are measured under zero and external magnetic fields using powdered and single crystalline specimens. To a considerable degree, the charge compensation between La and Co works in the equal (La, Co)-codoped case, where more than half of the Co ions are considered to be present in the minority spin sites at the center of the oxygen tetrahedra, with the = 3/2 state carrying a small orbital moment owing to spin-orbit interaction. The remaining small number of high-spin Co ( = 3/2, = 1) ions with unquenched orbital moments would be distributed to the other octahedral , , and sites.

High-pressure-high-temperature study of benzene; Refined crystal structure and new phase diagram up to 8 GPa and 923 K

Chanyshev, A. D.*; Litasov, K. D.*; Rashchenko, S.*; Sano, Asami; Kagi, Hiroyuki*; Hattori, Takanori; Shatskiy, A. F.*; Dymshits, A. M.*; Sharygin, I. S.*; Higo, Yuji*

Crystal Growth & Design, 18(5), p.3016 - 3026, 2018/05

https://doi.org/10.1021/acs.cgd.8b00125

The high-temperature structural properties of solid benzene were studied at 1.5-8.2 GPa up to melting or decomposition using multi-anvil apparatus and in situ neutron and X-ray diffraction. The crystal structure of deuterated benzene phase II (P2/c unit cell) was refined at 3.6-8.2 GPa and 473-873 K. Our data show a minor temperature effect on the change in the unit cell parameters of deuterated benzene at 7.8-8.2 GPa. At 3.6-4.0 GPa, we observed the deviation of deuterium atoms from the benzene ring plane and minor zigzag deformation of the benzene ring, enhancing with the temperature increase caused by the displacement of benzene molecules and decrease of van der Waals bond length between the -conjuncted carbon skeleton and the deuterium atom of adjacent molecule. Deformation of benzene molecule at 723-773 K and 3.9-4.0 GPa could be related to the benzene oligomerization at the same conditions. In the pressure range of 1.5-8.2 GPa, benzene decomposition was defined between 773-923 K. Melting was identified at 2.2 GPa and 573 K. Quenched products analyzed by Raman spectroscopy consist of carbonaceous material. The defined benzene phase diagram appears to be consistent with those of naphthalene, pyrene, and coronene at 1.5-8 GPa.

Bulk moduli and equations of state of ice VII and ice VIII

Klotz, S.*; Komatsu, Kazuki*; Kagi, Hiroyuki*; Kunc, K.*; Sano, Asami; Machida, Shinichi*; Hattori, Takanori

Physical Review B, 95(17), p.174111_1 - 174111_7, 2017/05

AA2017-0082.pdf:0.79MB

https://doi.org/10.1103/PhysRevB.95.174111

The compression behaviour of deuterated ice VII and VIII was investigated by high pressure neutron scattering in the pressure range 2-13.7 GPa between 93 K and 300 K. We establish equations-of-state which contain accurate values for the bulk moduli B, their pressure derivatives B', as well as the ambient pressure volumina V. These equations-of-state hold over a large part of the stability domain of ice VII, by comparison with available X-ray data, and to at least 13 GPa for ice VIII. They are indistinguishable at low pressures, but beyond 7 GPa and at low temperatures ice VIII appears to become stiffer than expected. This might be related to an anomalous phonon hardening observed previously in ice VIII in this range [D.D. Klug et al., Physical Review B, 70, 144113 (2004)].

Ice VII from aqueous salt solutions; From a glass to a crystal with broken H-bonds

Klotz, S.*; Komatsu, Kazuki*; Pietrucci, F.*; Kagi, Hiroyuki*; Ludl, A.-A.*; Machida, Shinichi*; Hattori, Takanori; Sano, Asami; Bove, L. E.*

Scientific Reports (Internet), 6, p.32040_1 - 32040_8, 2016/08

https://doi.org/10.1038/srep32040

It has been known since decades that certain aqueous salt solutions of LiCl and LiBr readily form glasses when cooled to below 160 K. This fact has recently been exploited to produce a salty high pressure ice form: When the glass is compressed at low temperatures to pressures higher than 4 GPa and subsequently warmed, it crystallizes into ice VII with the ionic species trapped inside the ice lattice. Here we report the extreme limit of salt incorporation into ice VII, using high pressure neutron diffraction and molecular dynamics simulations. We show that high-pressure crystallization of aqueous solutions of LiCl5.6HO and LiBr5.6HO leads to solids with strongly expanded volume, a destruction of the hydrogen-bond network with an isotropic distribution of water-dipole moments, as well as a crystal to-amorphous transition on decompression. This highly unusual behavior constitutes an interesting pathway from a glass to a crystal where translational periodicity is restored but the rotational degree of freedoms remaining completely random.

Design and performance of high-pressure PLANET beamline at pulsed neutron source at J-PARC

Hattori, Takanori; Sano, Asami; Arima, Hiroshi*; Komatsu, Kazuki*; Yamada, Akihiro*; Inamura, Yasuhiro; Nakatani, Takeshi; Seto, Yusuke*; Nagai, Takaya*; Utsumi, Wataru; et al.

Nuclear Instruments and Methods in Physics Research A, 780, p.55 - 67, 2015/04

https://doi.org/10.1016/j.nima.2015.01.059

PLANET is a time-of-flight (ToF) neutron beamline dedicated to high-pressure and high-temperature experiments. The large six-axis multi-anvil high-pressure press designed for ToF neutron diffraction experiments enables routine data collection at high pressures and high temperatures up to 10 GPa and 2000 K, respectively. To obtain clean data, the beamline is equipped with the incident slits and receiving collimators to eliminate parasitic scattering from the high-pressure cell assembly. The high performance of the diffractometer for the resolution ( / 0.6%) and the accessible -spacing range (0.2-8.4 ) together with low-parasitic scattering characteristics enables precise structure determination of crystals and liquids under high pressure and temperature conditions.