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

Ba 8Si 39Ge 7 and Ba 8Si 29Ge 17 have been studied at high pressure using x-ray diffraction and x-ray absorption spectroscopy (XAS) at the Ge K edge. In Ba 8Si 39Ge 7, a transition is observed similar to the one in Ba 8Si 46, 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 Ba 8Si 29Ge 17, such phase transition is not observed as the Ba atoms appear already off-center at ambient pressure.
Authors:
ORCiD logo [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
Publication Date:
Report Number(s):
LA-UR-17-22102
Journal ID: ISSN 2469-9950
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 93; Journal Issue: 13; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Material Science; Clathrates, pressure, phase transition, silicon, germanium
OSTI Identifier:
1351200

Blancon, Jean-Christophe Robert, Machon, Denis, Pischedda, Vittoria, Debord, Regis, Toulemonde, Pierre, Le Floch, Sylvie, Pascarelli, Sakura, Melinon, Patrice, and San-Miguel, Alfonso. Revisiting pressure-induced phase transition in silicon clathrates using Ge substitution. United States: N. p., Web. doi:10.1103/PhysRevB.93.134103.
Blancon, Jean-Christophe Robert, Machon, Denis, Pischedda, Vittoria, Debord, Regis, Toulemonde, Pierre, Le Floch, Sylvie, Pascarelli, Sakura, Melinon, Patrice, & San-Miguel, Alfonso. Revisiting pressure-induced phase transition in silicon clathrates using Ge substitution. United States. doi:10.1103/PhysRevB.93.134103.
Blancon, Jean-Christophe Robert, Machon, Denis, Pischedda, Vittoria, Debord, Regis, Toulemonde, Pierre, Le Floch, Sylvie, Pascarelli, Sakura, Melinon, Patrice, and San-Miguel, Alfonso. 2016. "Revisiting pressure-induced phase transition in silicon clathrates using Ge substitution". United States. doi:10.1103/PhysRevB.93.134103. https://www.osti.gov/servlets/purl/1351200.
@article{osti_1351200,
title = {Revisiting pressure-induced phase transition in silicon clathrates using Ge substitution},
author = {Blancon, Jean-Christophe Robert and Machon, Denis and Pischedda, Vittoria and Debord, Regis and Toulemonde, Pierre and Le Floch, Sylvie and Pascarelli, Sakura and Melinon, Patrice and San-Miguel, Alfonso},
abstractNote = {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.},
doi = {10.1103/PhysRevB.93.134103},
journal = {Physical Review B},
number = 13,
volume = 93,
place = {United States},
year = {2016},
month = {4}
}