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Physics and Chemistry of Minerals

, Volume 27, Issue 8, pp 575–582 | Cite as

Structural evolution of rutile-type and CaCl2-type germanium dioxide at high pressure

  • J. Haines
  • J. M. Léger
  • C. Chateau
  • A. S. Pereira
ORIGINAL PAPER

Abstract

 Germanium dioxide was found to undergo a transition from the tetragonal rutile-type to the orthorhombic CaCl2-type phase above 25 GPa. The detailed structural evolution of both phases at high pressure in a diamond anvil cell has been investigated by Rietveld refinement using angle-dispersive, X-ray powder-diffraction data. The square of the spontaneous strain (ab)/(a+b) in the orthorhombic phase was found to be a linear function of pressure and no discontinuities in the cell constants and volume were observed, indicating that the transition is second-order and proper ferroelastic. Compression of the GeO6 octahedra was found to be anisotropic, with the apical Ge-O distances decreasing to a greater extent than the equatorial distances and becoming shorter than the latter above 7 GPa. Above this pressure, the GeO6 octahedron exhibits the common type of tetragonal distortion predicted by a simple ionic model and observed for most rutile-type structures such as those of the heavier group-14 dioxides and the metal difluorides. Above the phase transition, the columns of edge-sharing octahedra tilt about their two fold axes parallel to c and the rotation angle reaches 10.2(5)° by 36(1) GPa so as to yield a hexagonal close-packed oxygen sublattice. The compressibility increases at the phase change as is expected for a second-order transition at which an additional compression mechanism becomes available.

Key words Germanium dioxide High pressure phase transition Rietveld refinement 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • J. Haines
    • 1
  • J. M. Léger
    • 1
  • C. Chateau
    • 1
  • A. S. Pereira
    • 1
  1. 1.Laboratoire de physico-chimie des matériaux, CNRS, 1, Place Aristide Briand 92190 Meudon, France e-mail: Haines@cnrs-bellevue.fr Tel.: +33-1-45075511 Fax: +33-1-45075910FR

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