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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：10 Percentile：74.02(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.
AsIkeda, Shugo*; Tsuchiya, Yu*; Zhang, X.-W.*; Kishimoto, Shunji*; Kikegawa, Takumi*; Yoda, Yoshitaka*; Nakamura, Hiroki; Machida, Masahiko; Glasbrenner, J.*; Kobayashi, Hisao*
Physical Review B, 98(10), p.100502_1 - 100502_6, 2018/09
Times Cited Count：6 Percentile：25.82(Materials Science, Multidisciplinary)The interplay between magnetism and superconductivity is one of important subjects to investigate the pairing mechanism in novel superconductors. We have found new coexistence between an antiferromagnetic order in the Fe sublattice and superconductivity of the FeAs-based EuFeAs superconductor in the pressure range from 2.4 to 3.0 GPa by 
Fe nuclear forward scattering (NFS) using a single crystal sample. The magnetic state in the Fe sublattice changes to a new antiferromagnetic one with superconductivity from a stripe-type antiferromagnetic one observed in normal conducting state at 2.7 GPa. Below the superconducting transition temperature, the temperature dependence of Fe NFS spectra reveals that the new antiferromagnetic order develops with the superconductivity. This non-trivial coupling of two ordered states in EuFeAs under pressure demonstrates a new and intriguing relationship between magnetism and superconductivity in Fe-based superconductors.
-type oxide PbZnOMori, Daisuke*; Tanaka, Kie*; Saito, Hiroyuki; Kikegawa, Takumi*; Inaguma, Yoshiyuki*
Inorganic Chemistry, 54(23), p.11405 - 11410, 2015/12
Times Cited Count：28 Percentile：81.65(Chemistry, Inorganic & Nuclear)Sano, Asami; Yagi, Takehiko*; Okada, Taku*; Goto, Hirotada*; Kikegawa, Takumi*
Physics and Chemistry of Minerals, 39(5), p.375 - 383, 2012/05
Times Cited Count：20 Percentile：55.17(Materials Science, Multidisciplinary)X-ray diffraction measurements of distorted rutile-type oxyhydroxides 
-GaOOH, InOOH, -CrOOH, and -CrOOD were taken at a maximum pressure of up to 35 GPa under quasi-hydrostatic conditions, at ambient temperature. Anomalies in the evolution of the relative lattice constants and the axial ratios of -GaOOH, InOOH, and -CrOOD suggest anisotropic stiffening along the a- and/or b-axes where the hydrogen bond is formed. The changes were observed at 15 GPa in -GaOOH and InOOH and at 4 GPa in -CrOOD. The pressures were higher in oxyhydroxides that have longer O...O distances of the hydrogen bond at ambient pressure. In contrast, such stiffening behavior was not observed in CrOOH, which has a significant short O...O distance and strong hydrogen bond. The stiffening behaviors observed in the present study can be attributed to the symmetrization of the hydrogen bonds in oxyhydroxides, as was previously found in 
-AlOOH(D).
Hattori, Takanori; Taga, Naohito*; Takasugi, Yukinobu*; Kinoshita, Tomohiro*; Narushima, Takashi*; Tsuji, Kazuhiko*; Kikegawa, Takumi*
Photon Factory Activity Report 2005, Part A, p.42 - 43, 2006/11
no abstracts in English
X-ray diffraction of graphite-diamond transformation using various catalysts under high pressures and high temperaturesUtsumi, Wataru; Okada, Taku; Taniguchi, Takashi*; Funakoshi, Kenichi*; Kikegawa, Takumi*; Hamaya, Nozomu; Shimomura, Osamu
Journal of Physics; Condensed Matter, 16(14), p.S1017 - S1026, 2004/04
Times Cited Count：14 Percentile：54(Physics, Condensed Matter)The graphite-diamond transformation was investigated using in-situ time-resolved X-ray diffraction experiments with a MgO dissolved aqueous fluid as the diamond forming catalyst under conditions of 6.6-8.8 GPa and 1400-1835
C. Experiments were conducted using a 180-ton DIA-type cubic-anvil apparatus installed on the beamline BL14B1 at SPring-8, a third-generation synchrotron radiation facility in Japan. By analyzing the kinetic data using the JMAK rate equation, it was clarified that altering the pressure-temperature conditions drastically changes the nucleation and growth process of diamond.
Otaka, Osamu*; Utsumi, Wataru; Kikegawa, Takumi*
Mirai O Hiraku Koatsuryoku Kagaku Gijutsu Semina Shirizu, 27, p.52 - 62, 2003/07
no abstracts in English
and HfO under high-temperature and high-pressureOtaka, Osamu*; Fukui, Hiroyuki*; Funakoshi, Kenichi*; Utsumi, Wataru; Irifune, Tetsuo*; Kikegawa, Takumi*
High Pressure Research, 22(1), p.221 - 226, 2002/01
Times Cited Count：30 Percentile：76.07(Physics, Multidisciplinary)no abstracts in English
SiO
Kubo, Tomoaki*; Otani, Eiji*; Kato, Takumi*; Urakawa, Satoru*; Suzuki, Akio*; Kambe, Yuichi*; Funakoshi, Kenichi*; Utsumi, Wataru; Kikegawa, Takumi*; Fujino, Kiyoshi*
Physics of the Earth and Planetary Interiors, 129(1-2), p.153 - 171, 2002/01
Times Cited Count：50 Percentile：66.4(Geochemistry & Geophysics)no abstracts in English
under high pressure and high peratureOtaka, Osamu*; Fukui, Hiroyuki*; Kunisada, Taichi*; Fujisawa, Tomoyuki*; Funakoshi, Kenichi*; Utsumi, Wataru; Irifune, Tetsuo*; Kuroda, Koji*; Kikegawa, Takumi*
Physical Review B, 63(17), p.174108_1 - 174108_8, 2001/05
Times Cited Count：127 Percentile：96.62(Materials Science, Multidisciplinary)no abstracts in English
Yagi, Takehiko*; Kondo, Tadashi*; Watanuki, Tetsu; Shimomura, Osamu; Kikegawa, Takumi*
Review of Scientific Instruments, 72(2), p.1293 - 1297, 2001/02
Times Cited Count：28 Percentile：78.2(Instruments & Instrumentation)no abstracts in English
Eto, Tetsujiro*; Endo, Shoichi*; Imai, Motoharu*; Katayama, Yoshinori; Kikegawa, Takumi*
Physical Review B, 61(22), p.14984 - 14988, 2000/06
Times Cited Count：51 Percentile：87.97(Materials Science, Multidisciplinary)The pressure effect on the lattice constant of NiO with the rhombohedral distorted B1 structure was studied up to 141 GPa by 
angle-dispersive x-ray diffraction using synchrotron radiation, an imaging plate, and a diamond anvil cell. The lattice constant 
and 
, expressed in the hexagonal lattice, decrease monotonously with increasing pressure. The axial rage 
decreases monotonously with increasing pressure, indicating the distortion in the rhombohedral [111] direction becomes larger as pressure increases. The signiifcant change of above 60 GPa, suggested by a recent theoretical calculation, was not observed.
under high-temperature and high-pressure conditionsFukui, Hiroyuki*; Otaka, Osamu*; Katsura, Tomoo*; Nagai, Takaya*; Funakoshi, Kenichi*; Utsumi, Wataru; Kikegawa, Takumi*
Science and Technology of High Pressure, p.554 - 557, 2000/00
no abstracts in English
Eto, Tetsujiro*; Endo, Shoichi*; Imai, Motoharu*; Katayama, Yoshinori; Kikegawa, Takumi*
Science and Technology of High Pressure (Proceedings of AIRAPT-17), p.487 - 490, 2000/00
The pressure effect on the lattice constant of NiO with the rhombohedral distorted B1 structure was studied up to 141 GPa by angle-dispersive x-ray diffraction using synchrotron radiation and an imaging plate, with reference to a recent theoretical calculation within the density-functional formalism with the local-spin density approcximation. The lattice constant and , expressed in the hexagonal lattice, decrease monotonously with increasing pressure. The axial rage decreases monotonously with increasing pressure, indicating the enhancement of the rhombohedral distortion. The signiifcant change of above 60 GPa suggested by the calculation was not observed.
Irifune, Tetsuo*; Kuroda, Koji*; Nishiyama, Norimasa*; Inoue, Toru*; Funamori, Nobumasa*; Uchida, Takeyuki*; Yagi, Takehiko*; Utsumi, Wataru; Miyajima, Nobuyoshi*; Fujino, Kiyoshi*; et al.
Geophysical Monograph 101 (Properties of Earth and Planetary Materials at High Pressure and Temperature), p.1 - 8, 1998/00
no abstracts in English
Katayama, Yoshinori; Tsuji, Kazuhiko*; Shimomura, Osamu; Kikegawa, Takumi*; M.Mezouar*; D.Martinez-Garcia*; J.M.Besson*; D.Haeusermann*; M.Hanfland*
Journal of Synchrotron Radiation, 5(Part3), p.1023 - 1025, 1998/00
no abstracts in English
Taniguchi, Takashi*; Sato, Masashi*; Utsumi, Wataru; Kikegawa, Takumi*; Shimomura, Osamu
Diamond and Related Materials, 6(12), p.1806 - 1815, 1997/12
Times Cited Count：17 Percentile：69.66(Materials Science, Multidisciplinary)no abstracts in English
Taniguchi, Takashi*; Sato, Masashi*; Utsumi, Wataru; Kikegawa, Takumi*; Shimomura, Osamu
Applied Physics Letters, 70(18), p.2392 - 2394, 1997/05
Times Cited Count：25 Percentile：74.65(Physics, Applied)no abstracts in English
Yaoita, Kenichi*; Katayama, Yoshinori; Tsuji, Kazuhiko*; Kikegawa, Takumi*; Shimomura, Osamu
Review of Scientific Instruments, 68(5), p.2106 - 2110, 1997/05
Times Cited Count：34 Percentile：87.27(Instruments & Instrumentation)An optical device called a multichannel collimator (MCC) was developed to rapidly perform an angle-dispersive diffraction using a multi-anvil press (MAP) with synchrotron radiation. The MCC consists of multiple channels of collimators in a radial alignment. This eliminates diffraction from the materials surrounding the sample so that we can obtain high-quality diffraction from samples in a MAP using an imaging plate. We have installed a MCC system on a MAP named MAX90 at the Photon Factory, National Laboratory for High Energy Physics. Performance of the MCC has been satisfactorily evaluated, and diffraction patterns of liquid sodium and liquid gallium under 4.8 GPahave been succesfully obtained using this system.
OOH oxyhydroxide and implication for hydrogen bond symmetrizationSano, Asami; Yagi, Takehiko*; Okada, Taku*; Goto, Hirotada*; Kagi, Hiroyuki*; Nagai, Takaya*; Kikegawa, Takumi*
no journal, ,
