Hydrogen vibration excitations of ZrH and TiH up to 21 GPa by incoherent inelastic neutron scattering

Hattori, Takanori; Nakamura, Mitsutaka; Iida, Kazuki*; Machida, Akihiko*; Sano, Asami; Machida, Shinichi*; Arima, Hiroshi*; Oshita, Hidetoshi*; Honda, Takashi*; Ikeda, Kazutaka*; et al.

Physical Review B, 106(13), p.134309_1 - 134309_9, 2022/10

https://doi.org/10.1103/PhysRevB.106.134309

Hydrogen vibration excitations of fluorite-type ZrH and TiH were investigated up to 21 GPa and 4 GPa, respectively, by incoherent inelastic neutron scattering experiments. The first excitation energies increased with pressure, as described by the equations (meV) = 141.4(2) + 1.02(2)(GPa) and (meV) = 149.4(1) + 1.21(8)(GPa) for ZrH and TiH, respectively. Coupling with pressure dependence of lattice parameters, the relations between metal-hydrogen distance () and are found to be well described by the equations (meV) = 1.62(9) 10 ((meV) = 1.47(21) 10 (AA), respectively. The slopes of these curves are much steep compared to the previously reported trend in various fluorite-type metal hydrides at ambient pressure. The hydrogen wave function spreading showed that the local potential field for a hydrogen atom shrinks more intensively than the tetrahedral site. These behavior is likely caused by the rigid metal ion core and the resulting confinement of the hydrogen atom in the narrower potential field at high pressures.

Displacement of hydrogen position in di-hydride of V-Ti-Cr solid solution alloys

Sakaki, Koji*; Kim, H.*; Majzoub, E. H.*; Machida, Akihiko*; Watanuki, Tetsu*; Ikeda, Kazutaka*; Otomo, Toshiya*; Mizuno, Masataka*; Matsumura, Daiju; Nakamura, Yumiko*

Acta Materialia, 234, p.118055_1 - 118055_10, 2022/08

https://doi.org/10.1016/j.actamat.2022.118055

Magnetic structure of short-range ordering in intermetallic antiferromagnet MnRhSi

Kodama, Katsuaki; Honda, Takashi*; Yamauchi, Hiroki; Shamoto, Shinichi*; Ikeda, Kazutaka*; Otomo, Toshiya*

Journal of the Physical Society of Japan, 90(7), p.074710_1 - 074710_7, 2021/07

https://doi.org/10.7566/JPSJ.90.074710

Local- and intermediate-range order in room temperature superionic conducting Ag-GeSe glasses

Hosokawa, Shinya*; Kawakita, Yukinobu; Stellhorn, J. R.*; Pusztai, L.*; Blanc, N.*; Boudet, N.*; Ikeda, Kazutaka*; Otomo, Toshiya*

JPS Conference Proceedings (Internet), 33, p.011070_1 - 011070_7, 2021/03

BB2019-1957.pdf:3.47MB

https://doi.org/10.7566/JPSCP.33.011070

Local- and intermediate-range atomic order in Ag ion conducting glasses Ag(GeSe) with x = 0.15, 0.28, 0.33, and 0.50 were investigated by using a combination of AXS, XRD, ND, and RMC modeling. By adding the ND pdf to AXS and XRD results, reasonable partial structure factors and partial pdf were obtained by the RMC procedure. In contrast to the previous AXS and RMC study, a large number of Ag-Ge and Ge-Ge correlations are observed in the first coordination shell region, which is consistent with an MD simulation. The coordination numbers around the Ge and Se mostly follow the 8- rule over all Ag concentrations if Ag is not taken into account. With increasing the Ag concentration, the partial coordination numbers with Ge and Se atoms around Ag remarkably increases, while the Ag-Ag coordination number increases only slightly, indicating that the Ag conducting path is formed through the second neighboring Ag-Ag correlations.

Distance-selected topochemical dehydro-diels-alder reaction of 1,4-Diphenylbutadiyne toward crystalline graphitic nanoribbons

Zhang, P.*; Tang, X.*; Wang, Y.*; Wang, X.*; Gao, D.*; Li, Y.*; Zheng, H.*; Wang, Y.*; Wang, X.*; Fu, R.*; et al.

Journal of the American Chemical Society, 142(41), p.17662 - 17669, 2020/10

https://doi.org/10.1021/jacs.0c08274

Solid-state topochemical polymerization (SSTP) is a promising method to construct functional crystalline polymeric materials, but in contrast to various reactions that happen in solution, only very limited types of SSTP reactions are reported. Diels-Alder (DA) and dehydro-DA (DDA) reactions are textbook reactions for preparing six-membered rings in solution but are scarcely seen in solid-state synthesis. Here, using multiple cutting-edge techniques, we demonstrate that the solid 1,4-diphenylbutadiyne (DPB) undergoes a DDA reaction under 10-20 GPa with the phenyl as the dienophile. The crystal structure at the critical pressure shows that this reaction is "distance-selected". The distance of 3.2 between the phenyl and the phenylethynyl facilitates the DDA reaction, while the distances for other DDA and 1,4-addition reactions are too large to allow the bonding. The obtained products are crystalline armchair graphitic nanoribbons, and hence our studies open a new route to construct the crystalline carbon materials with atomic-scale control.

Strong lattice anharmonicity exhibited by the high-energy optical phonons in thermoelectric material

Wu, P.*; Fan, F.-R.*; Hagihara, Masato*; Kofu, Maiko; Peng, K.*; Ishikawa, Yoshihisa*; Lee, S.*; Honda, Takashi*; Yonemura, Masao*; Ikeda, Kazutaka*; et al.

New Journal of Physics (Internet), 22(8), p.083083_1 - 083083_9, 2020/08

https://doi.org/10.1088/1367-2630/aba98f

Thermoelectric material SnSe has aroused world-wide interests in the past years, and its inherent strong lattice anharmonicity is regarded as a crucial factor for its outstanding thermoelectric performance. However, the understanding of lattice anharmonicity in SnSe system remains inadequate, especially regarding how phonon dynamics are affected by this behavior. In this work, we present a comprehensive study of lattice dynamics on NaSnSeS by means of neutron total scattering, inelastic neutron scattering, Raman spectroscopy as well as frozen-phonon calculations. Lattice anharmonicity is evidenced by pair distribution function, inelastic neutron scattering and Raman measurements. By separating the effects of thermal expansion and multi-phonon scattering, we found that the latter is very significant in high-energy optical phonon modes. The strong temperature-dependence of these phonon modes indicate the anharmonicity in this system. Moreover, our data reveals that the linewidths of high-energy optical phonons become broadened with mild doping of sulfur. Our studies suggest that the thermoelectric performance of SnSe could be further enhanced by reducing the contributions of high-energy optical phonon modes to the lattice thermal conductivity via phonon engineering.

Structural and electrochemical features of (LiS)(SiS) superionic glasses

Mori, Kazuhiro*; Iwase, Kenji*; Oba, Yojiro; Ikeda, Kazutaka*; Otomo, Toshiya*; Fukunaga, Toshiharu*

Solid State Ionics, 344, p.115141_1 - 115141_10, 2020/01

https://doi.org/10.1016/j.ssi.2019.115141

no abstracts in English

Nanoscale ice-type structural fluctuation in spinel titanates

Torigoe, Shuhei*; Hattori, Takayuki*; Kodama, Katsuaki; Honda, Takashi*; Sagayama, Hajime*; Ikeda, Kazutaka*; Otomo, Toshiya*; Nitani, Hiroaki*; Abe, Hitoshi*; Murakawa, Hiroshi*; et al.

Physical Review B, 98(13), p.134443_1 - 134443_7, 2018/10

https://doi.org/10.1103/PhysRevB.98.134443

Alternative equation on magnetic pair distribution function for quantitative analysis

Kodama, Katsuaki; Ikeda, Kazutaka*; Shamoto, Shinichi; Otomo, Toshiya*

Journal of the Physical Society of Japan, 86(12), p.124708_1 - 124708_8, 2017/12

https://doi.org/10.7566/JPSJ.86.124708

Investigation and measures of abnormal events of helium refrigerator for cryogenic hydrogen system at J-PARC

Aso, Tomokazu; Teshigawara, Makoto; Hasegawa, Shoichi; Aoyagi, Katsuhiro*; Muto, Hideki*; Nomura, Kazutaka*; Takada, Hiroshi; Ikeda, Yujiro

JAEA-Technology 2017-021, 75 Pages, 2017/08

JAEA-Technology-2017-021.pdf:33.03MB

Liquid hydrogen is employed as a cold neutron moderator material at the spallation neutron source of Materials and Life science experimental Facility of Japan Proton Accelerator Research Complex (J-PARC). From January 2015, it became observable that the differential pressure between heat exchangers and an 80 K adsorber (ADS) in a helium refrigerator system increased with operating time. In November 2015, the differential pressure rise became more significant, leading to degrade the refrigerating performance in cooling liquid hydrogen. In order to investigate the cause of the abnormal differential pressure rise between the heat exchangers and the ADS, we carried out visual inspection inside the heat exchangers and analyzed the impurities contained in the helium gas. Unfortunately, we could not identify the impurities causing the performance degradation, but observed a trace of oil in the inlet piping of the heat exchanger. Based on investigations of the abnormal events occurred in the refrigerators with similar refrigerating capacity at other facilities, we took measures that cleaning the heat exchangers with Freon and replacing the ADS with new one. As a result, the differential pressure rise phenomenon was removed to recover the performance. We have detected oil from the Freon used for cleaning the heat exchangers and at a felt supporting charcoal packed in the ADS. In particular, oil was accumulated in membranous form onto the felt at the entrance side in the ADS. The amount of oil contained in the helium gas was about 10 ppb or so, less than the design value, in the helium refrigerator. However, the oil accumulated onto the felt in the ADS through long operating period may cause abnormal differential pressure rise, leading to the performance degradation of the helium refrigerator. Further study is needed to specify the cause more clearly.