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baddeleyite involving softenings of bulk modulus and atom vibrationsFukui, Hiroshi*; Fujimoto, Manato*; Akahama, Yuichi*; Sano, Asami; Hattori, Takanori
Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 75(4), p.742 - 749, 2019/08
Times Cited Count：9 Percentile：63.29(Chemistry, Multidisciplinary)Monoclinic ZrO baddeleyite exhibits anomalous softenings of bulk modulus and atom vibrations with compression. We have investigated the pressure evolution of the structure by neutron powder diffraction combined with ab-initio calculations. The present results showed that the anomalous pressure response of the bulk modulus is related not to the change in the bonding characters but to the deformation of an oxygen sublattice, especially one of layers made of oxygens in the crystallographic 
* plane. The layer consists of two parallelograms; one is rotating with little distortion and the other is being distorted with increasing pressure. This deformation of this layer makes one of Zr-O distances long, resulting in the softening of some atom vibrational modes.
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：71 Percentile：90.29(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.
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.
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：51 Percentile：84.47(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
octahedron in the high-density liquid is more compressible than that in solids.
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：4 Percentile：26.08(Physics, Condensed Matter)no abstracts in English
glass under pressureOtaka, 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：64.18(Physics, Condensed Matter)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：76.59(Physics, Multidisciplinary)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：129 Percentile：96.71(Materials Science, Multidisciplinary)no abstracts in English
under pressureOtaka, 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
Fukui, Hiroyuki*; Otaka, Osamu*; Nagai, Takaya*; Katsura, Tomoo*; Funakoshi, Kenichi*; Utsumi, Wataru
Physics and Chemistry of Minerals, 27(6), p.367 - 370, 2000/06
Times Cited Count：4 Percentile：21.52(Materials Science, Multidisciplinary)no abstracts in English
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
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, 
, at ambient pressure has two maxima at 2A
and 3A. 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.
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, , at ambient pressure has two maxima at 2A and 3A. 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.
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
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.
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.
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.
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.
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.
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.
