Pressure-induced collapse of the guest EU off-centering in type-I clathrate EU8Ga16Ge30

Naoki Ishimatsu, Kei Yokoyama, Takahiro Onimaru, Toshiro Takabatake, Koichiro Suekuni, Naomi Kawamura, Satoshi Tsutsui, Masaichiro Mizumaki, Toshiaki Ina, Tetsu Watanuki, Vera Cuartero, Olivier Mathon, Sakura Pascarelli, Eiji Nishibori, Tetsuo Irifune

Research output: Contribution to journalArticlepeer-review

Abstract

We have revealed the pressure-induced collapse of the guest Eu off-centering in type-I clathrate Eu8Ga16Ge30 by the measurements of extended X-ray absorption fine structure (EXAFS) at the Ge K-edge in a temperature range of 10–300 K. Our analysis of the EXAFS spectra at ambient pressure confirmed that the guest Eu is located in the off-centered positions at Δoffset = 0.39(1) Å away from the center of the Ga=Ge tetradodecahedron cage (14-cage). However, with applying pressure to 13.1 GPa, Δoffset decreases to zero, and the atomic density of Eu is concentrated near the center of the 14-cage with a broad distribution. The present result demonstrates a close relationship between Δoffset and the size of the cage: Δoffset decreases when the 14-cage shrinks by applying pressure. With further compression, we have observed a drastic change in the EXAFS spectra due to amorphization. In the amorphous phase, the first nearest neighbor Ge–Ga=Ge bond is longer than in the crystal phase, whereas the guest Eu atom is located randomly with respect to the Ge atoms.

Original languageEnglish
Article number114601
Journaljournal of the physical society of japan
Volume88
Issue number11
DOIs
Publication statusPublished - 2019

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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