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Fe
O
solid solutions under high-pressure and high-temperature conditionsYamanaka, 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
Times Cited Count：0 Percentile：0.02(Materials Science, Multidisciplinary)Magnetic and crystal structure of MnFeO solid solutions under high-PT conditions are investigated by neutron diffraction and synchrotron M
ssbauer spectroscopy. The ferrimagnetic-paramagnetic transition and tetragonal-cubic transition of Mn
FeO spinel occur at 100
C and 180C, respectively, suggesting both the transitions are not coupled. The structure transition temperature decreases with pressure. Mssbauer experiments and neutron diffraction revealed that the Fe
occupancy in tetrahedral site increases increase with pressure, suggesting MnFeO phase approaches inverse spinel. Magnetic structure refinement clarified paramagnetic and ferrimagnetic structure of MnFeO and MnFeO. These spinels transform into high-pressure orthorhombic phases at 18.4 and 14.0 GPa, respectively, indicating lower transition pressure with increasing Mn content.
Yamashita, Keishiro*; Komatsu, Kazuki*; Klotz, S.*; Fabelo, O.*; Fern
ndez-D
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
Times Cited Count：0 Percentile：0(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.
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
Times Cited Count：1 Percentile：63.35(Physics, Multidisciplinary)Ouchi, Kazuki; Komatsu, Atsushi; Takao, Koichiro*; Kitatsuji, Yoshihiro; Watanabe, Masayuki
Chemistry Letters, 50(6), p.1169 - 1172, 2021/06
Times Cited Count：0 Percentile：0(Chemistry, Multidisciplinary)The electrochemical behavior of uranium (IV) tetrachloride in ionic liquid-DMF mixture was studied for first time in order to build a redox flow battery (RFB) using U as an electrode active material. We found a quasi-reversible U
/U
couple that could be applied to the anode reaction of the RFB.
Nakano, Satoshi*; Sano, Asami; Hattori, Takanori; Machida, Shinichi*; Komatsu, Kazuki*; Fujihisa, Hiroshi*; Yamawaki, Hiroshi*; Goto, Yoshito*; Kikegawa, Takumi*
Inorganic Chemistry, 60(5), p.3065 - 3073, 2021/03
Times Cited Count：7 Percentile：84.3(Chemistry, Inorganic & Nuclear)X-ray and neutron diffraction analyses of ammonia borane were conducted at ambient and high pressures. The H-H distance in dihydrogen bonds was shorter than twice the van der Waals radius (2.4 
). The half of the dihydrogen bonds were broken on phase transition from AP to the first high pressure phase (HP1) at approximately 1.2 GPa as revealed by an increase in the H-H distances. On further pressure increase, all of the H-H distances became shorter than 2.4 again, implying the pressure-induced reformation of the dihydrogen bonds. Furthermore, the HP1 transformed to the second one with the structure of 
(Z = 2) at about 11 GPa. In this phase transition, the inclination of the molecule axis became larger and the number of types of dihydrogen bonds increased from 6 to 11. Just before the third transition at 18.9 GPa, the shortest dihydrogen bond decreased to 1.65 . The present study experimentally first confirmed the breakage and reformation of the dihydrogen bonds by the structural change under pressure.
Miao, P.*; Tan, Z.*; Lee, S. H.*; Ishikawa, Yoshihisa*; Torii, Shuki*; Yonemura, Masao*; Koda, Akihiro*; Komatsu, Kazuki*; Machida, Shinichi*; Sano, Asami; et al.
Physical Review B, 103(9), p.094302_1 - 094302_18, 2021/03
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)The layered perovskite PrBaCo
O
demonstrates a strong negative thermal expansion (NTE) which holds potential for being fabricated into composites with zero thermal expansion. The NTE was found to be intimately associated with the spontaneous magnetic ordering, known as magneto-volume effect (MVE). Here we report with compelling evidences that the continuous-like MVE in PrBaCoO is intrinsically of discontinuous character, originating from an magnetoelectric transition from an antiferromagnetic insulating large-volume (AFILV) phase to a ferromagnetic less-insulating small-volume (FLISV) phase. Furthermore, the magnetoelectric effect (ME) shows high sensitivity to multiple external stimuli such as temperature, carrier doping, hydrostatic pressure, magnetic field etc. In contrast to the well-known ME such as colossal magnetoresistance and multi-ferroic effect which involve symmetry breaking of crystal structure, the ME in the cobaltite is purely isostructural. Our discovery provides a new path way to realizing the ME as well as the NTE, which may find applications in new techniques.
)Komatsu, Kazuki*; Iwasaki, Tsugumi*; Murata, Kosuke*; Yamashiro, Hideaki*; Goh, V. S. T.*; Nakayama, Ryo*; Fujishima, Yohei*; Ono, Takumi*; Kino, Yasushi*; Shimizu, Yoshinaka*; et al.
Reproduction in Domestic Animals, 56(3), p.484 - 497, 2021/03
Times Cited Count：8 Percentile：93.7(Agriculture, Dairy & Animal Science)We have established an archive system of livestock and wild animals from the surrounding ex-evacuation zone. Wildlife within the alert zone have been exposed to low-dose-rate (LDR) radiation for a long and continuous time. In this study, we analysed the morphological characteristics of the testes and in vitro fertilization (IVF) capacity of cryopreserved sperm of raccoons from the ex-evacuation zone of the FDNPP accident. This study revealed that the chronic and LDR radiation exposure associated with the FDNPP accident had no adverse effect on the reproductive characteristics and functions of male raccoons.
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
Times Cited Count：16 Percentile：87.13(Multidisciplinary Sciences)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.
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).
Bauer, R.*; Tse, J. S.*; Komatsu, Kazuki*; Machida, Shinichi*; Hattori, Takanori
Nature, 585(7825), p.E9 - E10, 2020/09
Times Cited Count：4 Percentile：89.27(Multidisciplinary Sciences)Pressure-induced structural transformations in deuterated crystalline ice-Ih were studied in-situ at 100 K using neutron diffraction. Very long relaxation time was allowed between small pressure increments to promote transformations to the thermodynamic stable high pressure crystalline phases. The results contradict a recent report in which measurements under similar temperature and pressure environment show successive crystal-to-crystal transformations (Tulk, et.al., Nature 2019). Instead, ice Ih was found to transform partially to an amorphous form (high density amorphous, HDA) at 1.0 GPa and then ice VII started to emerge at 1.5 GPa, a pressure substantially lower than all earlier studies. During this pressure interval, crystalline ice Ih or ice VII co-exist with HDA. The ice VII formed is stable upon pressure release down to 0.1 GPa. The very low compression rate has a profound effect on the crystallinity in the amorphous regime. Gathering all the existing experimental evidences allows an unambiguous description of the phenomenon of pressure induced amorphization. The onset of the phase transition is triggered by a shear instability of the ice lattice. The co-existence ice VII with HDA, instead of the equilibrium thermodynamic stable and proton-ordered ice-VIII under the same pressure-temperature condition reveals at low temperature there is insufficient thermal energy to overcome the substantial geometrical rearrangement from a single proton disordered H-bond network to an interpenetrating proton ordered H-bond crystalline network. Thus, leaving the proton disordered H-network intact. The analysis shows unequivocally that the structure obtained from the compression of ice is controlled by kinetics and dependent on the temperature.
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
Times Cited Count：15 Percentile：66.07(Multidisciplinary Sciences)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.
Komatsu, Kazuki*; Klotz, S.*; Nakano, Satoshi*; Machida, Shinichi*; Hattori, Takanori; Sano, Asami; Yamashita, Keishiro*; Irifune, Tetsuo*
High Pressure Research, 40(1), p.184 - 193, 2020/02
Times Cited Count：10 Percentile：74.3(Physics, Multidisciplinary)A new high pressure cells for neutron diffraction experiments using nano-polycrystalline anvil is presented. The cell design, off-line pressure generation tests and a gas-loading procedure for this cell are described. The performance is illustrated by powder neutron diffraction patterns of ice VII to 
82 GPa. We also demonstrate the feasibility of single crystal neutron diffraction experiments of Fe
O
at ambient conditions using this cell and discuss the current limitation and future developments.
without stacking disorder by evacuating hydrogen from hydrogen hydrateKomatsu, Kazuki*; Machida, Shinichi*; Noritake, Fumiya*; Hattori, Takanori; Sano, Asami; Yamane, Ryo*; Yamashita, Keishiro*; Kagi, Hiroyuki*
Nature Communications (Internet), 11, p.464_1 - 464_5, 2020/02
Times Cited Count：32 Percentile：88.21(Multidisciplinary Sciences)Water freezes below 0
C at ambient pressure ordinarily to ice I
, with hexagonal stacking sequence. Under certain conditions, ice with a cubic stacking sequence can also be formed, but ideal ice I without stacking-disorder has never been formed until recently. Here we demonstrate a route to obtain ice I without stacking-disorder by degassing hydrogen from the high-pressure form of hydrogen hydrate, C, which has a host framework isostructural with ice I. The stacking-disorder free ice I is formed from C via an intermediate amorphous or nano-crystalline form under decompression, unlike the direct transformations occurring in ice XVI from neon hydrate, or ice XVII from hydrogen hydrate. The obtained ice I shows remarkable thermal stability, until the phase transition to ice I at 250 K, originating from the lack of dislocations. This discovery of ideal ice I will promote understanding of the role of stacking-disorder on the physical properties of ice as a counter end-member of ice I.
Klotz, S.*; Komatsu, Kazuki*; Polian, A.*; Machida, Shinichi*; Sano, Asami; Iti
, J.-P.*; Hattori, Takanori
Physical Review B, 101(6), p.064105_1 - 064105_6, 2020/02
Times Cited Count：3 Percentile：28.5(Materials Science, Multidisciplinary)Manganese oxide (MnO) is a prototype of an antiferromagnetic Mott-insulator. Here we investigate the interplay of magnetic ordering and lattice distortion across the Nel temperature 
under pressure using neutron and X-ray diffraction. We find an increase of with a rate of 
= +4.5(5) K/GPa, an increase of the rhombohedral distortion 
by 
= +0.018/GPa, as well as a volume striction which is insensitive to pressure. These results allow to retrieve the dependence of the coupling constants 
and 
on interatomic distances and compare it to first-principles predictions. Antiferromagnetic diffuse scattering was observed up to 1.2 , and long-range magnetic order appears at room temperature at 42 GPa.
X-ray and neutron diffraction methodsYamashita, Keishiro*; Komatsu, Kazuki*; Hattori, Takanori; Machida, Shinichi*; Kagi, Hiroyuki*
Acta Crystallographica Section C; Structural Chemistry (Internet), 75(12), p.1605 - 1612, 2019/12
Times Cited Count：5 Percentile：54.54(Chemistry, Multidisciplinary)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.
to 34 GPaKlotz, S.*; Casula, M.*; Komatsu, Kazuki*; Machida, Shinichi*; Hattori, Takanori
Physical Review B, 100(2), p.020101_1 - 020101_5, 2019/07
Times Cited Count：9 Percentile：54.8(Materials Science, Multidisciplinary)Ytterbium dihydride (YbH) shows a well-known transition at 
16 GPa from a CaH-type structure to a high-pressure (high-
) phase with Yb at hcp sites and unknown H-positions. Here, we report its complete structure determination by neutron diffraction at 34 GPa. Hydrogen(deuterium) is located at 2
and 2
positions of space group 
, thus forming a high-symmetry "collapsed" close-packed lattice. The transition is sluggish and can be seen as a transfer of 1/2 of the hydrogen atoms from strongly corrugated H-layers to interstitial sites of the Yb-lattice. We demonstrate by first-principles calculations that the transition is related to a change from a completely filled 
-electron configuration to a fractional -hole (0.25 h) occupation in the high- phase. The 
charge transfer closes the gap at the transition and leads to a metallic ground state with sizeable electron-phonon interaction involving out-of-plane vibrational modes of interstitial hydrogen.
-AlOOH under mantle conditions using neutron diffractionSano, Asami; Hattori, Takanori; Komatsu, Kazuki*; Kagi, Hiroyuki*; Nagai, Takaya*; Molaison, J. J.*; Dos Santos, A. M.*; Tulk, C. A.*
Scientific Reports (Internet), 8(1), p.15520_1 - 15520_9, 2018/10
Times Cited Count：37 Percentile：93.38(Multidisciplinary Sciences)The pressure response of hydrogen bond in aluminous hydroxide -AlOOH, which is an important candidate for water carrier to the deep Earth in a subducting slab, was investigated using neutron diffraction under high pressure. The symmetrization of hydrogen bond in which hydrogen locates at the center between two oxygen atoms was observed directly for the first time. The present result indicates that the changes of mineral properties such as increase in bulk modulus and sound velocities, which were previously found, were induced by the symmetrization and disorder state that was also found at just below the symmetrization pressure. Even the symmetrization is a small change in the hydrogen location but it is playing an important role in determining the physical properties of minerals.
Ishii, Yusuke*; Komatsu, Kazuki*; Nakano, Satoshi*; Machida, Shinichi*; Hattori, Takanori; Sano, Asami; Kagi, Hiroyuki*
Physical Chemistry Chemical Physics, 20(24), p.16650 - 16656, 2018/06
Times Cited Count：3 Percentile：15.53(Chemistry, Physical)The structure of an aluminum layered hydroxide, boehmite (
-AlOOH), as a function of pressure was studied by using 
synchrotron X-ray and neutron diffraction. Peak broadening and subsequent splitting, which are only found for hkl (h 
0) peaks in the X-ray diffraction patterns above 25 GPa, are explained by stacking disorder accompanied with a continuously increasing displacement of the AlO octahedral layer along a-axis. This finding could be the first experimental result for the pressure-induced stacking disorder driven by the continuous layer displacement. The magnitude of the layer displacement was estimated from the X-ray scattering profile calculation based on the stacking disordered structure model. Hydrogen bond geometries of boehmite, obtained by structure refinements on the observed neutron diffraction patterns for deuterated sample up to 10 GPa, show linearly approaching O-D covalent and D
O hydrogen bond distances and they could merge below 26 GPa. The pressure-induced stacking disorder would make the electrostatic potential of hydrogen bonds asymmetric, yielding less chance for the proton-tunnelling.
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
Times Cited Count：28 Percentile：79.7(Materials Science, Multidisciplinary)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)].
-glycine under high pressureShinozaki, Ayako*; Komatsu, Kazuki*; Kagi, Hiroyuki*; Fujimoto, Chikako*; Machida, Shinichi*; Sano, Asami; Hattori, Takanori
Journal of Chemical Physics, 148(4), p.044507_1 - 044507_8, 2017/01
Times Cited Count：8 Percentile：44.64(Chemistry, Physical)Pressure-response on the crystal structure of deuterated -glycine was investigated at room temperature, using powder and single-crystal X-ray diffraction, and powder neutron diffraction measurements under high pressure. No phase change was observed up to 8.7 GPa, although anisotropy of the lattice compressibility was found. Neutron diffraction measurements indicated the distance of the intermolecular DO bond along with the 
-axis increase with compression up to 6.4 GPa. The distance of another DO bond along with the -axis decreased with increasing pressure, and became the shortest intermolecular hydrogen bond above 3 GPa. In contrast, the lengths of the bifurcated N-DO and C-DO hydrogen bonds, which are formed between the layers of the -glycine molecules along the 
-axis, decreased significantly with increasing pressure. The decrease of the intermolecular distances resulted in the largest compressibility of the -axis, compared to the other two axes. Hirshfeld analysis suggested that the reduction of the void region size, rather than shrinkage of the strong N-DO hydrogen bonds, occurred with compression.
