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Revisiting pressure-induced phase transition in silicon clathrates using Ge substitution

Journal Article · · Physical Review B
 [1];  [2];  [1];  [1];  [3];  [1];  [4];  [1];  [1]
  1. Univ. of Lyon (France); Univ. Claude Bernard Lyon, Villeurbanne (France). Inst. Lumiere Matiere
  2. Univ. of Lyon (France); Univ. Claude Bernard Lyon, Villeurbanne (France). Inst. Lumiere Matiere; Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Institut Néel, CNRS and Université Joseph Fourier, 25 Avenue des Martyrs, BP 166, F-38042 Grenoble Cedex 9, France
  4. European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble, France
+ Show Author Affiliations
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, Journal Name: Physical Review B Journal Issue: 13 Vol. 93; ISSN 2469-9950
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

36 MATERIALS SCIENCE
Clathrates
pressure
phase transition
silicon
germanium
Material Science