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Machida, Akihiko; Watanuki, Tetsu; Omura, Ayako*; Aoki, Katsutoshi; Takemura, Kenichi*
no journal, ,
Pressure induced structural transitions of rare-earth metal hydrides have been investigated under hydrostatic pressure at room temperature. Tri-hydride, YH
, exhibits a hexagonal metal lattice containing three hydrogen atoms per metal atom in the interstitial spaces: two hydrogen atoms at the tetrahedral sites and one hydrogen atom near the Y metal plane in the octahedral sites. We observed the pressure-induced structural transformation from the hexagonal metal lattice into a face-centered cubic (fcc) one through an intermediate state, which appears in the wide pressure span of 12-22 GPa. The obtained X-ray diffraction patterns in the intermediate state are represented by long-period rhombohedral structures. These long-period structures gradually transform toward the fcc metal lattice with successively increasing in the fcc-type component in a unit cell upon compression.
Hattori, Takanori; Tsuji, Kazuhiko*
no journal, ,
To reveal the effect of the covalent/ionic chemical bonding character on the pressure-induced structural changes, we have investigated the liquid structures of various tetrahedrally bonded materials under high pressure. The results have shown that these liquids show various high-pressure behaviors, depending on the covalent/ionic character. However, these results are based on the average structure. To observe partial structures is inevitable to understand the nature of the various structural changes in liquid compounds. For this purpose, we have developed the method to determine the partial structure in liquid compounds at high pressures using an anomalous X-ray scattering method and applied it to liquid AgI. The obtained partial structural functions are in good agreement with the results of ab-initio MD calculation, which supports the validity of the AXS method to investigate the chemical short-range order in the liquid compounds.
Igawa, Naoki; Taguchi, Tomitsugu; Fukazawa, Hiroshi; Yamauchi, Hiroki; Ishii, Yoshinobu*; Utsumi, Wataru
no journal, ,
The structural stabilities of clathrate hydrates are deeply related with the physical properties of inclusion gases. In this study, we carried out neutron powder diffraction measurements of CO
and Xe deuterohydrates and the diffraction data were analyzed by the combination of the Rietveld and the maximum entropy method (MEM) to clarify the motion of inclusion gases. The motions of CO and Xe molecules in the small cages show the different manner from those in the large cages. These motions have small temperature dependences, in contrast to the CH
hydrate case where the motion of CH molecules in the large cage shows large temperature dependence.
Ti)O
Saito, Hiroyuki; Kitada, Kazuya*; Kobune, Masafumi*; Adachi, Wataru*; Yazawa, Tetsuo*; Ishikawa, Kenya*; Hiranaga, Yoshiomi*; Cho, Yasuo*; Aoki, Katsutoshi
no journal, ,
Katayama, Yoshinori
no journal, ,
Energy-despersive X-ray diffraction method is commonly used for X-ray diffraction measurements using a cubic-type multi-anvil-press because good background elimination and short data acquisition time can be achieved simultaneously. However, diffraction intensity is affected by several energy-dependent factors. Because it is difficult to estimate these factors separately, Tsuji et al., proposed a new empirical method for determination of structure factor of liquids and glasses. Furthermore, Funakoshi et al., developed a Monte Carlo simulation code to carry out the procedure. But these analyses sometimes give unreasonable results. We improved the method by implementing a common normalization method in a new code. The obtained structure factors of silica glass and liquid water at ambient conditions agree well with those reported previously.
Kajimoto, Ryoichi; Nakamura, Mitsutaka; Yokoo, Tetsuya*; Nakajima, Kenji; Inamura, Yasuhiro; Takahashi, Nobuaki; Maruyama, Ryuji; Soyama, Kazuhiko; Shibata, Kaoru; Suzuya, Kentaro; et al.
no journal, ,
4SEASONS is one of the neutron chopper spectrometers in J-PARC/MLF. It is intended to provide very high counting rate up to 300 meV neutron energy with medium resolution (
% at 
) to efficiently collect weak inelastic signals from novel spin and lattice dynamics especially in high-
superconductors and related materials. To achieve this goal, the spectrometer equips advanced instrumental design such as an elliptic-shaped converging neutron guide coated with high-
(
-4) supermirror, long-length (2.5 m) 
He PSDs arranged cylindrically inside the vacuum scattering chamber. Furthermore, the spectrometer is ready for multi-incident-energy measurements by the repetition rate multiplication method with a special Fermi chopper, and polarization analysis with He spin filters. 4SEASONS is now under construction and will be ready to use in December 2008. In this paper, we show the design of 4SEASONS and current status of its construction.
Tamada, Taro; Honjo, Eijiro; Arai, Shigeki; Kuroki, Ryota
no journal, ,
The ligand-receptor interaction in the extracellular environment is essential for signal transduction of biological processes. We have focused on the structure/function relationships of these proteins. Granulocyte colony-stimulating factor (GCSF) has become an important cytokine for medical treatment of patients suffering from granulopoenia through regulating the maturation, proliferation, and differentiation of the precursor cells of neutrophilic granulocytes. We determined a crystal structure of the signaling complex between human GCSF and a ligand binding region of GCSF receptor (GCSF-R). We also determined additional structures of human cytokines and extracellular regions of cytokine receptors, where the complexation with an antibody fragment (Fab) was used for crystallization and structure determination.
Yoneda, Yasuhiro; Abe, Hiroshi; Oshima, Takeshi; Morimoto, Ryo*; Uchida, Hirohisa*
no journal, ,
We performed structure analysis of Mg-Fe alloy system prepared by mechanical alloying. For Mg concentrations up to about 15 mol%, mechanical alloying can produce single-phase bcc alloys. By using the conventional average structure analysis and X-ray pair-distribution function method, we can bridge the long-range and short-range order structure of Mg-Fe alloys. The substituted Mg atoms arranged randomly in the low-Mg composition, but Mg atoms came to have the order structure as the Mg composition increases.
Ohara, Takashi; Kusaka, Katsuhiro*; Hosoya, Takaaki*; Kurihara, Kazuo; Tomoyori, Katsuaki*; Niimura, Nobuo*; Tanaka, Ichiro*; Suzuki, Jiro*; Nakatani, Takeshi; Otomo, Toshiya*; et al.
no journal, ,
no abstracts in English
Shoyama, Yoshinari; Tamada, Taro; Takeuchi, Ayako*; Taura, Futoshi*; Shoyama, Yukihiro*; Morimoto, Satoshi*; Kuroki, Ryota
no journal, ,
Nb)O revealed by changing B-site randomnessOwada, Kenji; Hirota, Kazuma*; Terauchi, Hikaru*; Fukuda, Tatsuo; Tsutsui, Satoshi*; Baron, A. Q. R.*; Mizuki, Junichiro; Owa, Hidehiro*; Yasuda, Naohiko*
no journal, ,
Pb(InNb)O (PIN) varies among antiferroelectric (AFE), ferroelectric (FE) and relaxor states depending upon the perovskite B-site randomness. We studied the effects of this randomness on the dynamics of PIN by high resolution inelastic X-ray scattering using ordered PIN (AFE) and disordered PIN (relaxor) single crystals. We have found a clear softening of a transverse optic mode at the 
point in both the samples, indicating a robust and intrinsic ferroelectric instability regardless of the actual ground state. We interpret that AFE is stabilized only when In and Nb ions are spatially ordered enough to overwhelm the FE instability. As the B-site randomness becomes larger, AFE is suppressed and the FE ground state starts appearing. Ultimately, the randomness competes with the development of FE regions and blocks a long range FE order, which we believe yields polar nanoregions resulting in relaxor behaviors.
Hayashi, Makoto*; Fujishita, Hideshi*; Kanai, Takashi*; Yamada, Takahiro*; Igawa, Naoki; Kihara, Kuniaki*
no journal, ,
A phenomenological theory describes the temperature dependence of the order parameter Q, which is atomic shift in displacement structural phase transition and of strain e, which is coupled to Q, near a phase transition. Recently, Romero and Salje showed the strain obeys the quantum phenomenological theory below the temperature of the displacement structural phase transition. However, direct evaluation of the quantum phenomenological theory by measuring the order parameters in entire temperature is required to verify the effectiveness of the theory. We carried out the structural analysis of quartz by neutron powder diffraction in the temperature range of 10-250K. We found that the strain was in proportion to the squares of the displacement of the Si atom along the a-axis in the present temperature range. The effectiveness of the theory was directly verified by the atomic displacement.
Okazaki, Nobuo; Ohara, Takashi; Umino, Hisao*; Chatake, Toshiyuki*; Kurihara, Kazuo; Cachau, R. E.*; Blaber, M.*; Niimura, Nobuo*; Kuroki, Ryota
no journal, ,
Honjo, Eijiro; Adachi, Motoyasu; Tamada, Taro; Kuroki, Ryota
no journal, ,
Because human immunodeficiency virus type 1 protease (HIV-1PR, 99 amino acids) is involved in the maturation of HIV-1, it is a prime target for antiviral therapy of AIDS. In order to investigate precise structure-function relationship, we are planning to determine the structure of HIV-1PR including the information of hydrogen and hydrating water molecules using high resolution X-ray crystallography and neutron crystallography. For higher resolution neutron protein crystallography, it is necessary to exchange hydrogen (H) atoms with deuterium (D) atoms in order to reduce background noise derived from incoherent neutron scattering cross-section of hydrogen. Therefore, we have expressed fully deuterated HIV-1PR using commercially available perdeuterated medium. X-ray structures of non labeled and perdeuterated HIV-1PR were determined to 1.2 and 1.4
resolution, respectively, using crystals grown under the same conditions. Both structures did not show any significant changes.
Fujiwara, Satoru; Takezawa, Yasunori*; Sugimoto, Yasunobu*; Wakabayashi, Katsuzo*
no journal, ,
In neutron scattering and diffraction, information on internal fluctuations or a variation of scattering length density of molecules of interest can be extracted by the contrast variation technique. This contrast variation technique was applied to measurements of neutron fiber diffraction of muscles. The neutron fiber diffraction patterns of frog sartorius muscles were measured in the relaxed state and the rigor state, in various D2O concentrations. It was shown that there were variations in the scattering length density distribution in the unit cell of the muscle structure. Analysis of the equatorial reflections showed that the phase information of these reflections is obtained, that the density projected onto a plane perpendicular to the fiber axis of muscle is different between the thick filament region and the thin filament region, and that the projected density of the thick filament changes as the state of muscle changes from the relaxed state to the rigor state.
Shibata, Kaoru; Takahashi, Nobuaki; Tsukushi, Itaru*; Nakajima, Kenji; Arai, Masatoshi
no journal, ,
In this presentation, we will report the experimental results of thermal diffuse scattering (TDS) which occurs close to the Bragg reflections in time-of-flight neutron diffraction. We measured the thermal diffuse scatterings around some analyzer crystals Bragg peaks; pyrolitic graphite PG(002), perfect silicon Si(111) and natural green mica: Mica(006). Those experiments were performed on the diffraction counter bank of LAM-80ET: the indirect geometry crystal analyzer spectrometer installed at KENS; the pulsed neutron source in KEK, Japan, using scattering angles around 2th 160. deg.
Shamoto, Shinichi; Kodama, Katsuaki; Iikubo, Satoshi*; Taguchi, Tomitsugu
no journal, ,
Atomic pair distribution function (PDF) analysis is very powerful tool for the structural analysis of a nanomaterial, because the crystal structure cannot be well reproduced by a unit cell with periodic boundary condition due to the limited size. Recently, there are active researches about the structure determination of nanomaterials. Here, we will discuss three finite size effects on PDF. The fast one is the particle form factor effect. The second one is the small angle scattering effect. The last one is the particle-particle correlation effect.
Watanuki, Tetsu; Machida, Akihiko; Kawana, Daichi; Aoki, Katsutoshi; Tsai, A. P.*
no journal, ,
The phase study of a Cd-Yb 1/1 approximant crystal over a wide pressure and temperature range is crucial for the comparison study between periodic and quasi-periodic crystals. Our previous X-ray diffraction study revealed that the Cd4 tetrahedra, the most inner part of the atomic clusters, exhibit various structural ordering in the orientation sensitive to pressure and temperature. Five ordered phases appear in a P-T span up to 5.2 GPa and down to 10K. In this study we surveyed higher pressure region up to 30 GPa at room temperature. Single crystal diffraction experiments at SPring-8 (BL22XU) using a helium pressure medium in a diamond anvil cell elucidated that the crystal undergoes successive structural phase transition with an alternation of the period. The bcc phase at ambient pressure transformed to a 3-fold ordered phase at about 12 GPa, and to 4-fold one at about 20 GPa. These phases are different from those found at the previous study.
Kuroki, Ryota
no journal, ,
X-ray and neutron crystallography enables us to obtain accurate atomic positions within proteins. The structure of porcine pancreatic elastase (PPE) with its potent inhibitor (FR130180) was determined to 0.94 resolution by X-ray diffraction and 1.75 resolution by neutron diffraction. It was found that there are two characteristic hydrogen bonding interactions in which hydrogen atoms were confirmed. One is located between a catalytic aspartate and histidine, another is involved in the inhibitor recognition site. The structure of HIV-PR with its potent inhibitor (KNI-272) was also determined to 0.93 resolution by X-ray diffraction and 2.3 resolution by neutron diffraction. The ionization state of the catalytic residues were clarified to show that Asp125 is protonated and Asp25 is deprotonated. The ionization state and the location of hydrogen atoms of the catalytic residue in HIV-PR were firstly determined by neutron diffraction.