Phonon dispersion curves in the type-I crystalline and molten clathrate compound Eu8Ga16Ge30

Takumi Hasegawa; Masanori Inui; Takahiro Onimaru; Yukio Kajihara; Shinya Hosokawa; Yoichi Nakajima; Kazuhiro Matsuda; Toshiro Takabatake; Satoshi Hiroi; Hiroshi Uchiyama; Satoshi Tsutsui

doi:10.1088/1361-648X/acb0a5

Phonon dispersion curves in the type-I crystalline and molten clathrate compound Eu₈Ga₁₆Ge₃₀

J Phys Condens Matter. 2023 Jan 20;35(11). doi: 10.1088/1361-648X/acb0a5.

Authors

Affiliations

¹ Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8521, Japan.
² Department of Physics, Kumamoto University, Kumamoto 860-8555, Japan.
³ Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
⁴ Japan Synchrotron Radiation Research Institute (JASRI), Sayo-cho, Hyogo 679-5198, Japan.
⁵ Institute of Quantum Beam Science, Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki 316-8511, Japan.

PMID: 36603227
DOI: 10.1088/1361-648X/acb0a5

Abstract

The dynamic structure factorS(Q,E), whereQandEare momentum and energy transfer, respectively, has been measured for liquid Eu₈Ga₁₆Ge₃₀(EGG), using inelastic x-ray scattering. The excitation energy of the longitudinal acoustic mode in the liquid was scaled to that in liquid Ba₈Ga₁₆Sn₃₀(BGS) with the effective mass. This result means that the local structure in both liquids are similar. The longitudinal acoustic excitation energy of type-I clathrate compound EGG disperses faster than that in the liquid, suggesting that the interatomic force is weakened on melting. The lower energy excitation was observed in both liquid EGG and liquid BGS. In comparison with the longitudinal phonon dispersion in crystalline clathrate compound EGG obtained by density functional theory-based calculations, the lower energy in the liquid was found to be near the optical mode energy. The result indicates that the lower energy mode arises from the relative motion between Eu and (Ga, Ge) atoms.

Keywords: Eu8Ga16Ge30; crystalline; dispersions; inelastic x-ray scattering; liquid; phonons.