Ionic radii in fluorites

Vauchy, R.; 廣岡 瞬; 村上 龍敏

Materialia, 32, p.101934_1 - 101934_12, 2023/12

https://doi.org/10.1016/j.mtla.2023.101934

The construction of the fluorite unit-cell from the ionic radii of the constitutive species is proposed with the use of our hybrid model, considering flexible anion and cation radii. 27 binary and stoichiometric compounds crystallizing in this structure were investigated to find a correlation between the anion's radius as a function of the cation's size.

X-ray free electron laser observation of ultrafast lattice behaviour under femtosecond laser-driven shock compression in iron

佐野 智一*; 松田 智己*; 廣瀬 明夫*; 寺井 智之*; 掛下 智之*; 犬伏 雄一*; 佐藤 孝弘*; 矢橋 牧名*; 菖蒲 敬久; 他22名*

Scientific Reports (Internet), 13, p.13796_1 - 13796_10, 2023/08

https://doi.org/10.1038/s41598-023-40283-6

Over the past century, understanding the nature of shock compression of condensed matter has been a major topic. About 20 years ago, a femtosecond laser emerged as a new shock-driver. Unlike conventional shock waves, a femtosecond laser driven shock wave creates unique microstructures in materials. Therefore, the properties of this shock wave may be different from those of conventional shock waves. However, the lattice behaviour under femtosecond laser-driven shock compression has never been elucidated. Here we report the ultrafast lattice behaviour in iron shocked by direct irradiation of a femtosecond laser pulse, diagnosed using X-ray free electron laser diffraction. We found that the initial compression state caused by the femtosecond laser driven shock wave is the same as that caused by conventional shock waves. We also found, for the first time experimentally, the temporal deviation of peaks of stress and strain waves predicted theoretically. Furthermore, the existence of a plastic wave peak between the stress and strain wave peaks is a new finding that has not been predicted even theoretically. Our findings will open up new avenues for designing novel materials that combine strength and toughness in a trade-off relationship.

Experimental evidence for the significance of optical phonons in thermal transport of tin monosulfide

Wu, P.*; 村井 直樹; Li, T.*; 梶本 亮一; 中村 充孝; 古府 麻衣子; 中島 健次; Xia, K.*; Peng, K.*; Zhang, Y.*; et al.

New Journal of Physics (Internet), 25(1), p.013032_1 - 013032_11, 2023/01

https://doi.org/10.1088/1367-2630/acb3ed

The understanding of the lattice dynamics is essential for engineering the thermal transport properties in quantum materials. Based on the canonical point of view, acoustic phonons are believed to be the principal thermal carriers in heat flow. Here, in this work, optical phonons are elucidated to play a pivotal role in determining the lattice thermal conductivity in thermoelectric material SnS by using the state-of-the-art inelastic neutron scattering technique combined with first-principles calculations. Additionally, in contrast to acoustic phonons, optical phonons are observed to exhibit pronounced softening and broadening with temperature. Our observations not only shed light on the significance of the optical phonons in thermal transport but also provide a vital clue to suppress the propagation of optical phonons to optimize the thermoelectric performance of SnS.

Antiferromagnetism and mixed valency in the new Kondo lattice compound CeRhSn

Opletal, P.; Duverger-Ndellec, E.*; Miliyanchuk, K.*; Malick, S.*; Hossain, Z.*; Custers, J.*

Journal of Alloys and Compounds, 927, p.166941_1 - 166941_7, 2022/12

https://doi.org/10.1016/j.jallcom.2022.166941

Single crystals of a new ternary compound CeRhSn were synthesized by flux method and its crystal structure and magnetic properties were studied by single crystal X-ray diffraction and magnetic susceptibility, specific heat and resistivity measurements. CeRhSn crystallizes in a new monoclinic crystal structure, space group 2m (No. 11) with Z = 2 and lattice parameters = 9.8708(5) , = 4.5779(3) ; and = 14.2381(7) , = 109.535(5), and V = 606.35(6) . The structure exhibits three inequivalent Ce-sites. A striking structural motif is the tetragonal pyramid of Rh-ions surrounding the Ce2 yielding an extreme short Ce2-Rh1 spacing of = 2.7486(10) . This strong hint to mixed valent cerium behavior is supported by the entropy analysis. We argue that the Ce2-ion is in a nonmagnetic Ce state while the other 2 Ce-sites are in a trivalent state. At low temperatures these latter become partially Kondo screened ( 4 K) and order antiferromagnetic below = 2.31 K. The ordering is accompanied by a superzone gap-opening in direction of the magnetic propagation vector Q = (0, 0, l).

Novel coupled channel framework connecting the quark model and lattice QCD for the near-threshold states

Yang, Z.*; Wang, G.-J.*; Wu, J.-J.*; 岡 眞; Zhu, S.-L.*

Physical Review Letters, 128(11), p.112001_1 - 112001_6, 2022/03

https://doi.org/10.1103/PhysRevLett.128.112001

閾値近傍のハドロン共鳴を有限サイズの格子QCDのデータを用いて解析する新しい手法を提案し、正パリティのメソンのスペクトルに応用した。ハミルトニアン有効理論にクォーク模型,クォークペア生成,DK相互作用の情報を入れてベアな状態と散乱状態の結合を取り入れた。4個の状態のうち、との状態は散乱状態と強く混合する。一方で、とはほとんどベアなクォーク模型状態で記述できる。有限格子サイズでのレベル交差が再現されることを示した。

Tree cutting approach for domain partitioning on forest-of-octrees-based block-structured static adaptive mesh refinement with lattice Boltzmann method

長谷川 雄太; 青木 尊之*; 小林 宏充*; 井戸村 泰宏; 小野寺 直幸

Parallel Computing, 108, p.102851_1 - 102851_12, 2021/12

https://doi.org/10.1016/j.parco.2021.102851

GPUスーパコンピュータに対して格子ボルツマン法(LBM: lattice Botltzmann method)およびforest-of-octreesに基づくブロック構造型の局所細分化格子(LMR: local mesh refinement)を用いた空力解析コードを実装し、その性能を評価した。性能評価の結果、従来の空間充填曲線(SFC; space-filling curve)に基づく領域分割アルゴリズムでは、本空力解析において袖領域通信のコストが過大となることがわかった。領域分割の改善手法として本稿では挿し木法を提案し、領域分割の局所性とトポロジーを改善し、従来のSFCに基づく手法に比べて通信コストを1/31/4に削減した。強スケーリング測定では、最大で1.82倍の高速化を示し、128GPUで2207MLUPS(mega-lattice update per second)の性能を達成した。弱スケーリング測定では、8128GPUで93.4%の並列化効率を示し、最大規模の128GPU計算では44.73億格子点を用いて9620MLUPSの性能を達成した。

Anisotropic thermal lattice expansion and crystallographic structure of strontium aluminide within Al-10Sr alloy as measured by in-situ neutron diffraction

Liss, K.-D.*; Harjo, S.; 川崎 卓郎; 相澤 一也; 徐 平光

Journal of Alloys and Compounds, 869, p.159232_1 - 159232_9, 2021/07

AA2020-0822.pdf:1.94MB

https://doi.org/10.1016/j.jallcom.2021.159232

The aluminium strontium master alloy Al-10Sr has been investigated by in-situ neutron diffraction upon a heating-cooling cycle, revealing composition, crystallographic structure, lattice evolution and linear thermal expansion coefficients. Expansion of the Al matrix between (23.5 ... 26.7)10 K depends on temperature and fits well to the literature values, extrapolating to higher temperature at 800 K. Thermal expansion is highly anisotropic for tetragonal AlSr by a factor of 1.86 with values of 20.8 and 11.110 K in and -axis. The even large discrepancy to the Al matrix is prone to residual intergranular phase stresses, explaining the brittleness of such composite material. Upon first heating, recovery of the initially plastically deformed materials is observed until 600 K and 700 K, for AlSr and Al. Rietveld analysis refines the 4 Wyckoff positions of the 4/ crystal structure to = 0.39 revealing that local tetrahedrons are regular while local hexagons are stretched, in contrast to the literature. Its lattice parameters report to = 4.44240(48) , = 11.0836(15) at 300 K. Furthermore, the manuscript demonstrates full technical analysis of the neutron data. Findings feed into data bases and an outlook for improving mechanical properties of AlSr composites is given.

Development of cryogenic tensile testing apparatus for lattice strain measurement using synchrotron radiation for REBCO composite conductors

菅野 未知央*; 町屋 修太郎*; 菖蒲 敬久; 城 鮎美*; 梶原 堅太郎*; 中本 達志*

Superconductor Science and Technology, 33(8), p.085003_1 - 085003_10, 2020/08

https://doi.org/10.1088/1361-6668/ab953e

REBaCuO-delta (REBCO) composite tapes are candidate conductors for future accelerator magnets. Given that REBCO is a brittle oxide film, stress/strain management is important in the mechanical design of a magnet. Therefore, the strain state of a superconducting film should be predicted under various operating conditions. A quantum beam is a useful tool in evaluating the strain state of a superconducting material in a composite conductor. Although various cryogenic tensile testing machines, in combination with neutron beam and synchrotron radiation, have been developed, they are not necessarily optimized for measuring highly textured materials such as REBCO films. This study reports a novel cryogenic tensile testing apparatus that can be used at the beamline of a synchrotron radiation facility. In this system, a superconducting tape is cooled using a Gifford-McMahon (GM) cryocooler through 2.5 m long thermal links made of 5 N high-purity aluminum. This enables a compact cryogenic loading system that can be mounted on the goniometer of a beamline. Lattice strain measurements using synchrotron radiation were conducted at 40 K, 77 K, and 300 K for a commercially available (Y,Gd)BCO coated conductor at BL28B2 in SPring-8. The onset strain of film fracture determined from the lattice strain measurement at 77 K agreed well with the irreversible strain of critical current at the same temperature. The residual and fracture strain of the (Y,Gd)BCO film at 77 K was evaluated as well.

Spectrum of the charmed baryons in 2+1-flavor lattice QCD

Can, K. U.*; Bahtiyar, H.*; Erkol, G.*; Gubler, P.; 岡 眞; 高橋 徹*

JPS Conference Proceedings (Internet), 26, p.022028_1 - 022028_5, 2019/11

https://doi.org/10.7566/JPSCP.26.022028

格子QCDによる第一原理計算を用いて、チャームバリオンの基底および励起状態のスペクトルを求めた。

Finite temperature sum rules in the vector channel at finite momentum

Gubler, P.; 佐藤 大輔*

Physical Review D, 96(11), p.114028_1 - 114028_20, 2017/12

AA2017-0609.pdf:1.09MB

https://doi.org/10.1103/PhysRevD.96.114028

本論文ではベクター・チャンネルのlongitudinalとtransverse成分に関する厳密な和則を初めて導出する。和則は真空成分を差し引かれた有限温度のスペクトル関数について導出され、以前調べたゼロ運動量の場合の一般化である。論文の後半では導出した和則はいかにして格子QCDデータを使ったスペクトル関数の特定に用いることができるかを示す。