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Journal Articles

Observation of two fine structures related to the hidden order in the spectral functions of URu$$_2$$Si$$_2$$

Yoshida, Rikiya*; Fukui, Masaki*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Okawa, Mario*; Malaeb, W.*; Shin, S.*; Muraoka, Yuji*; Yokoya, Takayoshi*

Physical Review B, 85(24), p.241102_1 - 241102_4, 2012/06

 Times Cited Count:18 Percentile:59.58(Materials Science, Multidisciplinary)

Journal Articles

Electronic structure of U(Ru$$_{1-x}$$Rh$$_{x}$$)$$_2$$Si$$_2$$ studied by laser angle-resolved photoemission spectroscopy

Yoshida, Rikiya*; Nakamura, Yoshiaki*; Fukui, Masaki*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Okawa, Mario*; Shin, S.*; Hirai, Masaaki*; Muraoka, Yuji*; et al.

Journal of Physics; Conference Series, 273, p.012021_1 - 012021_4, 2011/02

 Times Cited Count:1 Percentile:34.07

Journal Articles

Signature of hidden order and evidence for periodicity modification in URu$$_2$$Si$$_2$$

Yoshida, Rikiya*; Nakamura, Yoshiaki*; Fukui, Masaki*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Okawa, Mario*; Shin, S.*; Hirai, Masaaki*; Muraoka, Yuji*; et al.

Physical Review B, 82(20), p.205108_1 - 205108_6, 2010/11

 Times Cited Count:61 Percentile:88.17(Materials Science, Multidisciplinary)

Journal Articles

Proton-production double-differential cross sections for 300-MeV and 392-MeV proton-induced reactions

Iwamoto, Hiroki; Imamura, Minoru*; Koba, Yusuke*; Fukui, Yoshinori*; Wakabayashi, Genichiro*; Uozumi, Yusuke*; Kin, Tadahiro; Iwamoto, Yosuke; Hohara, Shinya*; Nakano, Masahiro*

Physical Review C, 82(3), p.034604_1 - 034604_8, 2010/09

 Times Cited Count:12 Percentile:63.36(Physics, Nuclear)

We investigate proton-production double-differential cross sections (DDXs) for 300- and 392-MeV proton-induced reactions on O, V, Tb, Ta, Au, Pb, and Bi. Emitted proton energies are measured with stacked scintillator spectrometers by the $$Delta$$$$E$$-$$E$$ technique. Experimental results are compared with the intranuclear cascade (INC) and quantum molecular dynamics models. Although both models can reproduce spectral DDXs, there is a difference at the most forward and backward angles. The cause of these differences is discussed in terms of the refraction caused by the nuclear potential. Angular distributions of the present data are well accounted for by the Kalbach systematics plus INC one-step calculations. The quasi-free-scattering contribution increases with decreasing target mass and increasing emission energy.

Journal Articles

Structure of liquid water under high pressure up to 17 GPa

Katayama, Yoshinori; Hattori, Takanori; Saito, Hiroyuki; Ikeda, Takashi; Aoki, Katsutoshi; Fukui, Hiroshi*; Funakoshi, Kenichi*

Physical Review B, 81(1), p.014109_1 - 014109_6, 2010/01

 Times Cited Count:69 Percentile:90.03(Materials Science, Multidisciplinary)

The structure of liquid water was studied along the melting curve up to 17.1 GPa and 850 K by in situ X-ray diffraction. At low pressures, the local structure changed toward a simple liquid-like structure through an increase in the coordination number of water molecules. Once densely packed structure of water molecules was achieved around 4 GPa, the volume was reduced through the decrease of the intermolecular distance on further compression. Classical molecular dynamics simulations well reproduced the experimental results although the degree of agreement depended on pressure. Limitations of the pair potential model were discussed.

Journal Articles

High pressure and high temperature EXAFS and diffraction study of AgI (MS35)

Yoshiasa, Akira*; Arima, Hiroshi; Fukui, Hiroshi*; Okube, Maki*; Katayama, Yoshinori; Otaka, Osamu*

Nihon Kessho Gakkai-Shi, 51(1), p.66 - 69, 2009/02

We have determined a precise P-T phase diagram of AgI by high-temperature high-pressure synchrotron experiments. X-ray diffraction and X-ray absorption measurements were performed using a multi-anvil high pressure apparatus at SPring-8 synchrotron radiation facility. In a disordered rock-salt phase, Ag ions occupy both octahedral and tetrahedral sites. The occupancy of tetrahedral site has a maximum value, 20%, at 2 GPa. A change from rock-salt structure to disordered rock-salt structure is gradual in the X-ray diffraction measurements while it is clearly observed in the X-ray absorption measurements. Analysis of EXAFS Debye-Waller factor is useful because the force constant can be decided directly even at high pressure and high temperature. Pressure influences greatly the effective potential and anharmonicity decreases with increasing pressure.

Journal Articles

Pressure-induced sharp coordination change in liquid germanate

Otaka, Osamu*; Arima, Hiroshi*; Fukui, Hiroyuki*; Utsumi, Wataru; Katayama, Yoshinori; Yoshiasa, Akira*

Physical Review Letters, 92(15), p.155506_1 - 155506_4, 2004/04

 Times Cited Count:49 Percentile:84.27(Physics, Multidisciplinary)

Local structures around germanium in liquid germanate have been investigated by means of in situ X-ray absorption measurements up to 9 GPa at 1273 K. Liquid germanate consisting of tetrahedrally coordinated germanium contracts with increasing pressure without significant changes in the local structure up to 2.5 GPa and then shows an abrupt fourfold-to-sixfold coordination change around 3 GPa. The coordination change is completed below 4 GPa where upon a high-density liquid consisting of octahedrally coordinated germanium becomes stable. The GeO$$_{6}$$ octahedron in the high-density liquid is more compressible than that in solids.

Journal Articles

Anharmonic effective pair potentials of gold under high pressure and high temperature

Okube, Maki*; Yoshiasa, Akira*; Otaka, Osamu*; Fukui, Hiroyuki*; Katayama, Yoshinori; Utsumi, Wataru

Journal of Physics; Condensed Matter, 14(44), p.11511 - 11515, 2002/11

 Times Cited Count:3 Percentile:20.61(Physics, Condensed Matter)

no abstracts in English

Journal Articles

XAFS study of GeO$$_{2}$$ glass under pressure

Otaka, Osamu*; Yoshiasa, Akira*; Fukui, Hiroyuki*; Murai, Keiichiro*; Okube, Maki*; Takebe, Hitoshi*; Katayama, Yoshinori; Utsumi, Wataru

Journal of Physics; Condensed Matter, 14(44), p.10521 - 10524, 2002/11

 Times Cited Count:18 Percentile:64.29(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Phase relations of AgI under high pressure and high temperature

Otaka, Osamu*; Takebe, Hitoshi*; Yoshiasa, Akira*; Fukui, Hiroshi*; Katayama, Yoshinori

Solid State Communications, 123(5), p.213 - 216, 2002/08

 Times Cited Count:18 Percentile:64.29(Physics, Condensed Matter)

Using a multi-anvil high-pressure device and synchrotron radiation, X-ray ${it in situ}$ observations of AgI high pressure and high temperature up to 6.0 GPa and 1000 K have been performed to investigate the phase relations between $$alpha$$-AgI, rocksalt-type, disordered rocksalt-type, and liquid phases. The three phases of $$alpha$$-AgI, disordered rocksalt-type, and liquid meet in a triple point in the vicinity of 823 K and 1.3 GPa. The melting curve of the disordered rocksalt phase is linear with a positive slope. The transition between rocksalt and the disordered rocksalt phases is a broad and diffuse disordering type within the same structure. The formation of the disordered rocksalt phase has been hence estimated with the variation of a relative intensity ratio of (111) and (200) diffraction from the rocksalt phase. With increasing pressure the rocksalt phase becomes stabel at high temperature. At 6.0 GPa the rocksalt phase directly melts without the transition to the disordered rocksalt phase.

Journal Articles

Anharmonicity of gold under high-pressure and high-temperature

Okube, Maki*; Yoshiasa, Akira*; Otaka, Osamu*; Fukui, Hiroshi*; Katayama, Yoshinori; Utsumi, Wataru

Solid State Communications, 121(5), p.235 - 239, 2002/02

 Times Cited Count:11 Percentile:50.76(Physics, Condensed Matter)

In order to examine the pressure effect on the anharmonicity of Au, EXAFS spectra near Au $$L_{3}$$-edge were measured at the temperature range from 300 to 1000K under pressure up to 14GPa using large volume high-pressure devices and synchrotron radiation. The values of EXAFS Debye-Waller factors, $$sigma2$$ and $$sigma3$$, become smaller with increase of pressure, which indicates that the potential width become narrower with pressure. The anharmonic effective pair potentials of Au, $$V(u)=au^{2}/2!+bu^{3}/3!$$, at 0.1MPa, 6 and 14GPa have been calculated. The pressure dependence of the coefficient of thermal expansion has also been evaluated.

Journal Articles

Structual changes of quartz-type crystalline and vitreous GeO$$_{2}$$ under pressure

Otaka, Osamu*; Yoshiasa, Akira*; Fukui, Hiroyuki*; Murai, Keiichiro*; Okube, Maki*; Katayama, Yoshinori; Utsumi, Wataru; Nishihata, Yasuo

Journal of Synchrotron Radiation, 8(Part2), p.791 - 793, 2001/03

no abstracts in English

Oral presentation

Structure of water under ultra high pressure, 2

Katayama, Yoshinori; Hattori, Takanori; Fukui, Hiroshi*; Nozawa, Akifumi*; Funakoshi, Kenichi*

no journal, , 

Liquid water shows anomalous properties and these properties are attributed to a network structure formed by hydogen-bonded water molecules. Such an open strucutre due to the four-fold coordination is easily transformed to a denser structure by an increase of pressure. To study the structure of water under high pressure, we have carried out in-situ high-pressure high-temperature X-ray diffraction experiments in SPring-8, a large syncrotron radiation facility. In the previous study, we carried out X-ray diffraction measurements using a cubic-type multianvil press installed on BL14B1 and found that the structure of water changes to a simple structure which can be described by a hard shpare model. In this study, we used a Kawai-type double-stage press installed on BL04B1 and extended the maximum pressure to about 17 GPa. By using relatively large sample, 1.5 mm in diameter, high quality data with low background noise were obtained. The stcuture factor, $$S(Q)$$, at ambient pressure has two maxima at 2A$$^{-1}$$ and 3A$$^{-1}$$. With increasing pressure, these maxima merged and formed a sharp peak which is resembles that for a simple liquid. Futher compression shifted the peak to high-Q direction. The increase of density is attributed to an increase of coordination number up to a few GPa and then it is attributed to a decrease of inter-molecular distance at higher pressures.

Oral presentation

Structure of water under high pressure and high temperature

Katayama, Yoshinori; Hattori, Takanori; Fukui, Hiroshi*; Nozawa, Akifumi*; Funakoshi, Kenichi*

no journal, , 

Liquid water shows anomalous properties and these properties are attributed to a network structure formed by hydogen-bonded water molecules. To study the structure of water under high pressure, we have carried out in-situ high-pressure high-temperature X-ray diffraction experiments in SPring-8. In addition to the previous X-ray diffraction measurements using a cubic-type multianvil press installed on BL14B1, measurements up to about 17 GPa were successfully carried out using a Kawai-type double-stage press installed on BL04B1. The stcuture factor, $$S(Q)$$, at ambient pressure has two maxima at 2A$$^{-1}$$ and 3A$$^{-1}$$. With increasing pressure, these maxima merged and formed a sharp peak which is resembles that for a simple liquid. Futher compression shifted the peak to larger-Q direction. The increase of density is attributed to an increase of coordination number up to a few GPa and then it is attributed to a decrease of inter-molecular distance at higher pressures.

Oral presentation

Structure of water under high pressure

Katayama, Yoshinori; Hattori, Takanori; Saito, Hiroyuki; Fukui, Hiroshi*

no journal, , 

Liquid water shows unique properties and they are related to a network structure formed by hydrogen bonds. Simulation studies predicted that pressure induced drastic structural change, such as weakening of the hydrogen-bond network and molecular dissociation, in a pressure range from several GPa to several tens GPa. We have measured X-ray diffraction of liquid water up to about 9 GPa and 420$$^circ$$C using a cubic-type multi-anvil press on BL14B1 at SPring-8, a synchrotron radiation facility in Japan. The coordination number of water molecules increases rapidly to about 10 around 4 GPa while the intermolecular distance was almost constant. The structure of water evolves toward a simple structure which can be described by a hard sphere model with increasing pressure. This result is in agreement with that of a recent neutron scattering study.

Oral presentation

Structure of water under high pressure and temperature

Katayama, Yoshinori; Hattori, Takanori; Saito, Hiroyuki; Aoki, Katsutoshi; Fukui, Hiroshi*; Funakoshi, Kenichi*

no journal, , 

The unique properties of liquid water are related hydrogen bonded network structure. Simulation studies predicted drastic changes such as weakening of hydrogen-bonded network structure and molecular dissociation in a pressure range from a few GPa to a few tens GPa. We have measured in-situ X-ray diffraction of liquid water just above the melting temperature at pressures up to 17 GPa using a cubic-type multi-anvil press on BL14B1 beamline and a Kawai-type double-stage press on BL04B1 beamline at SPring-8 synchrotron radiation facility. Below 5 GPa, the coordination number of water molecules rapidly increased to about 9 while inter-molecular distance stayed almost constant. In other words, the local structure changed to a simple structure with increasing pressure. Above this pressure, the volume reduction was attributed to a decreased of inter-molecular distance.

Oral presentation

Structure of liquid water under high pressure and high temperature

Katayama, Yoshinori; Hattori, Takanori; Saito, Hiroyuki; Ikeda, Takashi; Aoki, Katsutoshi; Fukui, Hiroshi*; Funakoshi, Kenichi*

no journal, , 

Liquid water shows unique properties and they are related to a network structure formed by hydrogen bonds. The coordination number of water molecules is close to 4 at ambient condition. We have measured X-ray diffraction of liquid water under high-pressure and high-temperature conditions just above the melting line up to 9 GPa using a cubic-type multi-anvil press on BL14B1 and up to 17 GPa using a Kawai-type press at BL04B1 at SPring-8. The coordination number of water molecules increased rapidly to about 10 around 5 GPa while the intermolecular distance was almost constant. On further compression, the volume was reduced through the decrease of the intermolecular distance. Classical molecular dynamics simulations were also performed for comparison. They well reproduced the experimental results although the degree of agreement depended on pressure. These results are compared with results of previous neutron scattering, X-ray diffraction and first-principles molecular dynamics studies.

Oral presentation

Structure of water under high pressure and high temperature

Katayama, Yoshinori; Hattori, Takanori; Saito, Hiroyuki; Ikeda, Takashi; Aoki, Katsutoshi; Fukui, Hiroshi*; Tange, Yoshinori*; Funakoshi, Kenichi*

no journal, , 

We have measured X-ray diffraction of liquid water under high-pressure and high- temperature conditions up to 9 GPa using a cubic-type press on BL14B1 and up to 17 GPa using a Kawai-type press on BL04B1 at SPring-8. The pressure range has been extended to 20 GPa using sintered diamond anvils. The P-T range where the local structure transforms from an ice-like structure to a simple-liquid-like structure has been revealed with a help of first-principles molecular dynamics simulations.

Oral presentation

Structure of water under high temperature and pressure

Katayama, Yoshinori; Ikeda, Takashi; Hattori, Takanori; Saito, Hiroyuki; Aoki, Katsutoshi; Fukui, Hiroshi*; Tange, Yoshinori*; Funakoshi, Kenichi*

no journal, , 

Liquid water shows unique properties and they are related to the network structure formed by hydrogen bonds between water molecules. To study pressure dependence of structure of water, we measured X-ray diffraction of water up to 20 GPa using multi-anvil type presses in SPring-8. The coordination number of water molecules increased rapidly up to 4 GPa while maintaining the intermolecular distance. First-principles molecular dynamics simulations were also performed for high-density water. The obtained oxygen-oxygen radial distribution functions were in excellent agreement with the experimental results. Results of the simulations revealed that temperature was more important factor for the structural change. We have performed additional measurements at high temperatures. The calculated oxygen-oxygen radial distribution functions were again consistent with our experimental results. These studies clarified a pressure-temperature region where the significant structural change occurred.

Oral presentation

Structure of water under high pressure and high temperature

Katayama, Yoshinori; Yagafarov, O.; Ikeda, Takashi; Saito, Hiroyuki; Aoki, Katsutoshi; Hattori, Takanori; Fukui, Hiroshi*; Tange, Yoshinori*; Funakoshi, Kenichi*

no journal, , 

Liquid water at ambient pressure shows unique properties and they are related to the network structure formed by hydrogen bonds between water molecules. To study structural change in the liquid water under high-pressure and high-temperature conditions, we have measured X-ray diffraction of liquid water just above the melting line up to 20 GPa. Up to 4 GPa, the coordination number increased rapidly while the intermolecular distance changed slightly. First-principles molecular dynamics simulations were also performed for high-density water. Results of the simulations in a wide pressure- temperature range revealed that temperature was more important factor for the crossover between the hydrogen-bonded and simple liquid-like liquids. We have measured X-ray diffraction of water as a function of temperature. The experimental results supported the results of the simulation.

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