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Journal Articles

Anomaly of structural relaxation in complex liquid metal of bismuth; Dynamic correlation function of coherent quasi-elastic neutron scattering

Kawakita, Yukinobu; Kikuchi, Tatsuya*; Inamura, Yasuhiro; Tahara, Shuta*; Maruyama, Kenji*; Hanashima, Takayasu*; Nakamura, Mitsutaka; Kiyanagi, Ryoji; Yamauchi, Yasuhiro*; Chiba, Kaori*; et al.

Physica B; Condensed Matter, 551, p.291 - 296, 2018/12

 Times Cited Count:8 Percentile:49.07(Physics, Condensed Matter)

There are elemental liquid metals with complex structures far from the hard sphere (HS) packing model. Liquid Bi has an asymmetric first peak in the structure factors S(Q). The pair distribution function g(r) exhibits strange distance ratio of 1:2 between the first and the second peaks. Since a HS model with two kinds of radius produces asymmetry of the main peak in S(Q), existence of short-lived covalent bonds was discussed. Contrarily, modulation of the atomic distribution by the Friedel oscillations of shielding electrons around metallic ions was discussed. To examine its bonding nature from viewpoints of dynamic correlation functions, we have measured neutron quasielastic scattering of liquid Bi by using cold disk chopper spectrometer installed at MLF of J-PARC. The van Hove function revealed that the shoulder structure located at a longer side of the first peak in g(r) exhibits a longer relaxation time than the main structures such as the first and second peaks.

Oral presentation

Middle range inter-molecular orientation correlation of chlorine dioxide as molecular liquid

Shimakura, Hironori; Ogata, Norio*; Kawakita, Yukinobu; Ohara, Koji*; Kohara, Shinji*; Takeda, Shinichi*

no journal, , 

Chlorine dioxide has been used as a disinfectant of drinking water because of strong oxidizing activity against various microbial proteins. Chlorine dioxide has a boiling point of 283 K and a melting point of 214 K, and amber liquid at 273 K with density of 1.64. It is known that, in the solid phase, dimerization occurs due to interaction between Cl and O belonging to the neighboring molecule. Focusing onto the inter-molecular correlations of chlorine dioxide in the liquid state, we have measured high energy X-ray diffraction at 204 K and 273 K and performed reverse Monte Carlo (RMC) structure modeling based on the experimental structural data. In order to distinguish the orientational correlation by intermolecular interaction from the geometrical correlation, we compared the results of full RMC results with the structure model of free packing. As a result, its inter-molecular correlation, especially inter-molecular O-O correlation, becomes weak with increasing temperature.

Oral presentation

Dynamical structure analysis of liquid Se$$_{2}$$Br$$_{2}$$ using by neutron quasi-elastic scattering

Shimakura, Hironori; Kawakita, Yukinobu; Inamura, Yasuhiro; Kikuchi, Tatsuya; Ueno, Hiroki; Nakamura, Mitsutaka; Nakajima, Kenji; Kawamura, Seiko; Shibata, Kaoru; Arai, Masatoshi; et al.

no journal, , 

Chalcogen-halogen systems have low melting point when chalcogen and halogen proportion is 1:1. At this ratio, selenium bromide consists of chain molecule with Br-Se-Se-Br form, where the bond angle and the dihedral angle are about 104$$^{circ}$$ and 83$$^{circ}$$ respectively. Selenium bromide has strong inter-molecular correlation where each molecule doesn't have enough space to rotate freely due to molecular shape and high density. Quasi-elastic neutron scattering (QENS) of liquid Se$$_{2}$$Br$$_{2}$$ was performed at AMATERAS which installed in MLF/J-PARC. Measured temperatures were 298 K, 373 K and 473 K. It is interesting that S(Q,E) has two components, one is narrow and the other is broad, at specific Q value which represents inter-molecular correlation. We discussed these two components and the other analysis result of QENS spectrum.

Oral presentation

Low-energy dynamics of superionic conductor AgI investigated by inelastic neutron scattering measurements

Nakamura, Mitsutaka; Shimakura, Hironori; Ueno, Hiroki; Kawakita, Yukinobu; Arai, Masatoshi; Kawamura, Seiko; Nakajima, Kenji; Kikuchi, Tatsuya

no journal, , 

In order to elucidate the dynamical changes caused by differences in the structural phase of AgI which is a typical superionic conducting material, we carried out a detailed examination of the dynamical structure factor S(Q,E) obtained by inelastic neutron scattering measurements. Herein, we show that the intensity in a low-energy region (E $$<$$ 2 meV) at around 2 $AA$^{-1}$$ abruptly increases beyond 420 K, and the temperature-dependent behavior of this intensity is remarkably similar to that of dc ionic conductivity over a wide temperature range in the region of 420 K. A unified explanation of the ionic conduction mechanism in superionic materials may be established in terms of their characteristic low-energy excitations.

Oral presentation

Fluctuations in medium-range structure of Bi-based metallic liquid alloys

Ueno, Hiroki; Kawakita, Yukinobu; Ohara, Koji*; Shimakura, Hironori; Tahara, Shuta*; Kumara, L. S. R.*; Yamaguchi, Hiroshi*; Yasunaga, Akinori*; Wakisaka, Yuiko*; Ito, Masayoshi*; et al.

no journal, , 

Bi-Zn system has a phase diagram with a miscibility gap where critical point is at Bi$$_{15}$$Zn$$_{85}$$. It is known that concentration fluctuation increases on approaching to the miscibility gap. Earlier studies suggested that the miscibility gap is attributed to difference in atomic size between Bi and Zn. Recent developments of instrument and analysis technique enable us to deduce partial structures and demonstrate atomic configurations in liquid. We performed detailed analysis on medium-range structure in liquid Bi$$_{50}$$Zn$$_{50}$$ by using neutron diffraction data obtained by the two-axis diffractometer, HERMES, installed in JRR-3M, JAEA and, X-ray diffraction at BL08W beamline in SPring-8, Hyogo, Japan. 3D atomic structural model obtained by Revere Monte Carlo technique exhibits temperature evolution of concentration fluctuations in medium-range structure, which suggests that phase separation tendency appears even in the edge of the miscibility gap of liquid Bi-Zn.

Oral presentation

Construction status of the Si crystal analyzer backscattering type high energy resolution spectrometer DNA, 5

Shibata, Kaoru*; Takahashi, Nobuaki; Kawakita, Yukinobu; Kamazawa, Kazuya*; Yamada, Takeshi*; Ueno, Hiroki; Shimakura, Hironori; Nakajima, Kenji; Kambara, Wataru; Inamura, Yasuhiro; et al.

no journal, , 

no abstracts in English

Oral presentation

Dynamics of liquid Se$$_{2}$$Br$$_{2}$$, 2

Shimakura, Hironori; Kawakita, Yukinobu; Inamura, Yasuhiro; Kikuchi, Tatsuya; Ueno, Hiroki; Nakamura, Mitsutaka; Nakajima, Kenji; Kawamura, Seiko; Shibata, Kaoru*; Arai, Masatoshi; et al.

no journal, , 

no abstracts in English

Oral presentation

Quantitative analysis of dynamics in strongly-correlated molecular liquid Se$$_{2}$$Br$$_{2}$$

Shimakura, Hironori; Kawakita, Yukinobu; Inamura, Yasuhiro; Kikuchi, Tatsuya; Ueno, Hiroki; Nakamura, Mitsutaka; Kawamura, Seiko; Shibata, Kaoru*; Arai, Masatoshi; Takeda, Shinichi*

no journal, , 

Oral presentation

Developments of the Si crystal analyzer backscattering spectrometer DNA

Shibata, Kaoru*; Takahashi, Nobuaki; Kawakita, Yukinobu; Kamazawa, Kazuya*; Yamada, Takeshi*; Ueno, Hiroki; Shimakura, Hironori; Nakajima, Kenji; Kambara, Wataru; Inamura, Yasuhiro; et al.

no journal, , 

no abstracts in English

Oral presentation

The Analysis of inter-molecular orientation of Se$$_{2}$$Br$$_{2}$$

Shimakura, Hironori; Kawakita, Yukinobu; Ohara, Koji*; Wakisaka, Yuiko*; Kohara, Shinji*; Takeda, Shinichi*

no journal, , 

no abstracts in English

Oral presentation

The Construction report of the Si crystal analyzer near backscattering spectrometer, 6

Shibata, Kaoru*; Takahashi, Nobuaki; Kawakita, Yukinobu; Kamazawa, Kazuya*; Yamada, Takeshi*; Ueno, Hiroki; Shimakura, Hironori; Nakajima, Kenji; Kambara, Wataru; Inamura, Yasuhiro; et al.

no journal, , 

no abstracts in English

Oral presentation

Dynamical structure analysis of liquid Se$$_{2}$$Br$$_{2}$$

Shimakura, Hironori; Kawakita, Yukinobu; Inamura, Yasuhiro; Kikuchi, Tatsuya; Ueno, Hiroki; Nakamura, Mitsutaka; Nakajima, Kenji; Kawamura, Seiko; Shibata, Kaoru*; Arai, Masatoshi; et al.

no journal, , 

no abstracts in English

Oral presentation

Mechanism of the function expression caused by disordered structure

Kawakita, Yukinobu; Li, B.; Kawasaki, Takuro; Kikuchi, Tatsuya*; Kiyanagi, Ryoji; Inamura, Yasuhiro; Ohara, Takashi; Shibata, Kaoru; Kofu, Maiko; Nakamura, Mitsutaka; et al.

no journal, , 

Research results obtained in JAEA Project Research "Mechanism of the function expression caused by disordered structure" will be focused in this presentation. The purpose of this project is to reveal mechanism of the function expression of functional materials where randomness involved in crystalline structure plays an key role, by applying the method and analyses frequently used in random material physics. We will report the results of liquid bismuth with complex structure which was investigated by time-space correlation function, and low thermal conductivity in layered thermoelectric material and next-generation solar cell which was investigated by neutron inelastic scattering measurements.

Oral presentation

Time-space correlation function of liquid metals with complex static structure deduced from pulsed neutron experiment

Kawakita, Yukinobu; Kikuchi, Tatsuya*; Inamura, Yasuhiro; Tahara, Shuta*; Maruyama, Kenji*; Hanashima, Takayasu*; Nakamura, Mitsutaka; Kiyanagi, Ryoji; Yamauchi, Yasuhiro*; Chiba, Kaori*; et al.

no journal, , 

There are many polyvalent liquid metals with complex structure which cannot be reproduced by random packing model. To explain such complexity, coexistence of metallic and covalent bonds, dynamic model of short-lived covalent bonds, and quasi-crystal model where Peierls distortion still remains even in liquid phase have been proposed from structure analyses and theoretical calculations. To obtain concrete picture experimentally for complex structure, it is indispensable to measure dynamic structure with precise statistical accuracy. We performed inelastic neutron scattering of liquid bismuth by using AMATERAS installed at MLF in J-PARC and deduced its time-space correlation function. We got evidence that structure of Peierls distortion remains even in liquid by evaluating difference in relaxation time at specific atomic distances characterized by double layered structure.

Oral presentation

Structural relaxation and time-space correlation function of liquid metals with complex structure

Kawakita, Yukinobu; Kikuchi, Tatsuya*; Inamura, Yasuhiro; Tahara, Shuta*; Maruyama, Kenji*; Hanashima, Takayasu*; Nakamura, Mitsutaka; Kiyanagi, Ryoji; Yamauchi, Yasuhiro*; Chiba, Kaori*; et al.

no journal, , 

We have performed coherent quasielastic neutron scattering experiment for liquid polyvalent metals which has complicated static structure not reproduced by a hard-sphere packing model, by utilizing AMATERAS spectrometer in J-PARC. It has been considered that, for Bi and Sb, a double-layered structure originated from Peierls distortion which is seen in solid crystalline phase remains even in their liquid phases. We have succeeded in detection of such Peierls distortion structure in liquid by difference in structural relaxation time at corresponding charateristic interatomic distances in the deduced time-space correlation function.

Oral presentation

Real time and real space analysis for atomic dynamics in liquids

Kawakita, Yukinobu; Kikuchi, Tatsuya*; Inamura, Yasuhiro; Tahara, Shuta*; Maruyama, Kenji*; Hanashima, Takayasu*; Nakamura, Mitsutaka; Kiyanagi, Ryoji; Yamauchi, Yasuhiro*; Chiba, Kaori*; et al.

no journal, , 

We have developed analysis method to reduce the so-call van Hove function, a time-space correlation function, through the regularization method for coherent quasielastic neutron scattering (QENS) of liquids. In principle, the van Hove function in r-t space can be obtained by double Fourier transform from dynamic structure factor in Q-E space. Instead of a direct function estimation of the van Hove function through the regularization method which easily involves systematical deviation of the calculated dynamic structure factor from the experimental dynamic structure factor, we used a mediation function between them and estimated it through the regularization method. We will discuss with the properties of the mediation function and the obtained van Hove function and the calculated dynamic structure factor with an example of liquid metals with complex static structure such as Bi and Sb whose QENS were measured by AMATERAS spectrometer in J-PARC.

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