Structural and thermal confinement of Schwarz crystals revealed by neutron scattering at MLF
Dan Huang1, Huangliu Fu1, Meng Lyu2, Yuanwen Feng1, Ryoichi Kajimoto3, Mitsutaka Nakamura3, Takashi Honda4, Enke Liu2, Bing Li1, Xiuyan Li1,5, and Ke Lu1,5
1IMR, CAS, 2IOP, CAS, 3JAEA, 4KEK, 5LAM
Schwarz crystals represent an unusual structural state of metals, consisting of extremely fine nanograins confined by three-dimensional triply periodic minimal surface (TPMS) grain boundaries. Their grain-boundary network strongly constrains the grains, giving rise to exceptional thermal stability and unusual physical properties. To clarify the microscopic effects of this unique structure, neutron experiments were performed at MLF, J-PARC, using the NOVA total scattering diffractometer and the 4SEASONS Fermi-chopper spectrometer. Neutron pair distribution function (PDF) analysis using NOVA revealed broadened and split PDF peaks in Schwarz Cu and Pt, indicating distinct local atomic environments associated with compressed nanograins and TPMS grain-boundary regions (Fig. 1). Inelastic neutron scattering (INS) measurements using 4SEASONS further showed broadened phonon spectra and shifts of vibrational modes toward higher energies, demonstrating pronounced phonon hardening, particularly in Schwarz Pt (Fig. 2). These structural and lattice-dynamical features are closely linked to the unusual thermal transport of Schwarz crystals. At low temperatures, the lattice thermal conductivity exhibits an approximately linear temperature dependence, a behavior rarely observed in bulk metals. These findings establish a link between local atomic structure, lattice dynamics, and thermal transport, highlighting structural confinement as a potential strategy for tuning thermal properties in bulk metals. This work has recently been published in Physical Review Research [1].
[1] D. Huang, H. Fu, M. Lyu, et al., Phys. Rev. Research 8, 033017 (2026).
Fig.1. (a), (d) G(r) of Cu and Pt samples with different microstructures and temperatures. (b), (c), (e), and (f) Magnified views of specific peaks in panels (a) and (d), highlighting the splitting of PDF peaks at selected r regions.
Fig.2. Contour plots of S(Q, E) for (a) Cu and (b) Pt Schwarz samples as a function of momentum transfer Q and energy transfer E. Phonon density of states extracted from INS data at incident energy Ei = 50 meV for (c) Cu and (d) Pt samples.
◆ 論文等
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Dan Huang, Huangliu Fu, Meng Lyu, Yuanwen Feng, Ryoichi Kajimoto, Mitsutaka Nakamura, Takashi Honda, Enke Liu, Bing Li, Xiuyan Li, and Ke Lu, "Structural and thermal confinement of Schwarz crystals", Phys. Rev. Res. 8, 033017 (2026).
Sara Yamauchi, Shuki Torii, Kazuhiko Ikeuchi, Daichi Ueta, Kazuhiro Mori, Tetsuya R. Yokoo, and Shinichi Itoh, "Recent Developments in the Sample Environment at KEK Neutron Science Beamlines", JPS Conf. Proc. 45, 011028 (2026).
(3) 量子物性グループ
【 BL12高分解能チョッパー分光器HRC 】
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Sara Yamauchi, Shuki Torii, Kazuhiko Ikeuchi, Daichi Ueta, Kazuhiro Mori, Tetsuya R. Yokoo, and Shinichi Itoh, "Recent Developments in the Sample Environment at KEK Neutron Science Beamlines", JPS Conf. Proc. 45, 011028 (2026).
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【 BL23偏極中性子散乱装置POLANO 】
◆ 論文等
Sara Yamauchi, Shuki Torii, Kazuhiko Ikeuchi, Daichi Ueta, Kazuhiro Mori, Tetsuya R. Yokoo, and Shinichi Itoh, "Recent Developments in the Sample Environment at KEK Neutron Science Beamlines", JPS Conf. Proc. 45, 011028 (2026).
