Revisiting pressure-induced phase transition in silicon clathrates using Ge substitution
- Univ. of Lyon (France); Univ. Claude Bernard Lyon, Villeurbanne (France). Inst. Lumiere Matiere
- Univ. of Lyon (France); Univ. Claude Bernard Lyon, Villeurbanne (France). Inst. Lumiere Matiere; Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Institut Néel, CNRS and Université Joseph Fourier, 25 Avenue des Martyrs, BP 166, F-38042 Grenoble Cedex 9, France
- European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble, France
Ba8Si39Ge7 and Ba8Si29Ge17 have been studied at high pressure using x-ray diffraction and x-ray absorption spectroscopy (XAS) at the Ge K edge. In Ba8Si39Ge7, a transition is observed similar to the one in Ba8Si46, apparently isostructural. However, the XAS data analysis shows that the transformation is related to the off-centering of the Ba atoms. A theoretical model based on a Landau potential suggests that this transition is second order, with a symmetry-breaking mechanism related to the Ba displacement probably initiated by the vacancy creation or local distortion predicted theoretically. Lastly, this analysis gives a coherent picture of the phase transition mechanism. In the case of Ba8Si29Ge17, such phase transition is not observed as the Ba atoms appear already off-center at ambient pressure.
- Research Organization:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- AC52-06NA25396
- OSTI ID:
- 1351200
- Report Number(s):
- LA-UR-17-22102
- Journal Information:
- Physical Review B, Vol. 93, Issue 13; ISSN 2469-9950
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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