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Journal Articles

Mode distribution analysis for superionic melt of CuI by coherent quasielastic neutron scattering

Kawakita, Yukinobu; Kikuchi, Tatsuya*; Tahara, Shuta*; Nakamura, Mitsutaka; Inamura, Yasuhiro; Maruyama, Kenji*; Yamauchi, Yasuhiro*; Kawamura, Seiko; Nakajima, Kenji

JPS Conference Proceedings (Internet), 33, p.011071_1 - 011071_6, 2021/03

CuI is a well-known superionic conductor in a high temperature solid phase where the mobile cations migrate between interstitial sites in the f.c.c. sublattice formed by iodine ions. Even in the molten state, it shows several features suggesting collective or cooperative ionic motion. MD results show that Cu diffuses much faster than I. The Cu-Cu partial structure factor have a FSDP which indicates a medium-range ordering of Cu ions. Moreover the Cu-Cu partial pair distribution deeply penetrates into the nearest neighboring Cu-I shell. To reveal origin such anomalous behaviors of molten CuI, we performed quaiselastic neutron scattering (QENS) by the disk-chopper spectrometer AMATERAS at MLF, J-PARC. To interpret the total dynamic structure factor obtained from coherent QENS, the mode distribution analysis was applied. It is found that the motion of iodine is a kind of fluctuating within an almost local area while Cu ions diffuse much faster than iodine ions.

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.

Journal Articles

The Structure of molten CuCl; Reverse Monte Carlo modeling with high-energy X-ray diffraction data and molecular dynamics of a polarizable ion model

Alcaraz, O.*; Trull$`a$s, J.*; Tahara, Shuta*; Kawakita, Yukinobu; Takeda, Shinichi*

Journal of Chemical Physics, 145(9), p.094503_1 - 094503_7, 2016/09

 Times Cited Count:3 Percentile:14.34(Chemistry, Physical)

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

Temperature dependence of liquid structure of Bi-based binary alloys, 2

Ueno, Hiroki; Kawakita, Yukinobu; Ohara, Koji*; Tahara, Shuta*; Kohara, Shinji*; Ito, Masayoshi*; Takeda, Shinichi*

no journal, , 

no abstracts in English

Oral presentation

Micro structures in Bi-based metallic liquid alloys

Ueno, Hiroki; Kawakita, Yukinobu; Ohara, Koji*; Tahara, Shuta*; Kohara, Shinji*; Ito, Masayoshi*; Takeda, Shinichi*

no journal, , 

Oral presentation

Relaxation phenomena in superionic and molten cuprous iodide

Kawakita, Yukinobu; Tahara, Shuta*; Nakamura, Mitsutaka; Kikuchi, Tatsuya; Inamura, Yasuhiro; Maruyama, Kenji*; Nakajima, Kenji; Kawamura, Seiko; Yamauchi, Yasuhiro; Kambara, Wataru; et al.

no journal, , 

no abstracts in English

Oral presentation

Coherent dynamics of molten cuprous iodide

Kawakita, Yukinobu; Tahara, Shuta*; Kikuchi, Tatsuya; Nakamura, Mitsutaka; Inamura, Yasuhiro; Maruyama, Kenji*; Yamauchi, Yasuhiro; Nakajima, Kenji; Kawamura, Seiko; Kambara, Wataru; et al.

no journal, , 

no abstracts in English

Oral presentation

Dynamic correlation functions of CuI superionic melt

Kawakita, Yukinobu; Tahara, Shuta*; Kikuchi, Tatsuya; Nakamura, Mitsutaka; Inamura, Yasuhiro; Maruyama, Kenji*; Yamauchi, Yasuhiro; Nakajima, Kenji; Kawamura, Seiko; Kambara, Wataru; et al.

no journal, , 

no abstracts in English

Oral presentation

Intermediate range ordering in molten noble-metal halides

Tahara, Shuta*; Kawakita, Yukinobu

no journal, , 

no abstracts in English

Oral presentation

Static and dynamic structures of superionic melts of noble-metal salts

Kawakita, Yukinobu; Tahara, Shuta*

no journal, , 

Oral presentation

Ion dynamics of superionic Melt CuI

Kawakita, Yukinobu; Tahara, Shuta*; Kikuchi, Tatsuya; Nakamura, Mitsutaka; Inamura, Yasuhiro; Maruyama, Kenji*; Yamauchi, Yasuhiro*; Nakajima, Kenji; Kawamura, Seiko; Kambara, Wataru*

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.

Oral presentation

Understanding atomic diffusion by neutron scattering experiment; Prospects toward real time and real space analysis

Kawakita, Yukinobu; Kikuchi, Tatsuya*; Matsuura, Masato*; Kawasaki, Takuro; Kofu, Maiko; Tahara, Shuta*

no journal, , 

Materials and Life Science Experimental Facility (MLF) at J-PARC gives opportunities to use pulsed neutron beam to material science including fast ionic diffusion phenomena. DNA and AMATERAS spectrometers in MLF are quite useful to study atomic diffusion directly by quasielastic neutron scattering. We will focus relatively new analysis and experimental methods in this presentation such as mode distribution analysis and deduction of time-space correlation function which are both model free analysis, and possibility to detect an ionic channel in single crystal, with a few examples.

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