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(3 + 1)-dimensional structure refinement of the fresnoite framework-structure type compound Ba2TiGe2O8

Höche, Thomas ; Esmaeilzadeh, Saeid ; Uecker, Reinhard ; Lidin, Sven LU and Neumann, Wolfgang (2003) In Acta Crystallographica. Section B: Structural Science 59(2). p.209-216
Abstract

The incommensurately modulated structure of the fresnoite framework-structure type compound Ba2TiGe2O8 has been solved using a (3 + 1)-dimensional superspace approach. The structure is orthorhombic and adopts the superspace group Cmm2(0,β,1/2)s00 with β ≃ 0.635 at room temperature. The refinement was based on neutron powder diffraction data obtained from a powdered single crystal grown by Czochralski pulling. The modulation parameters that were obtained support the idea that frozen-in rigid-unit modes cause the modulation. The modulation is mainly manifested by positional displacements of O atoms. Barium ions are either eightfold, ninefold or tenfold coordinated in the one-dimensional modulated... (More)

The incommensurately modulated structure of the fresnoite framework-structure type compound Ba2TiGe2O8 has been solved using a (3 + 1)-dimensional superspace approach. The structure is orthorhombic and adopts the superspace group Cmm2(0,β,1/2)s00 with β ≃ 0.635 at room temperature. The refinement was based on neutron powder diffraction data obtained from a powdered single crystal grown by Czochralski pulling. The modulation parameters that were obtained support the idea that frozen-in rigid-unit modes cause the modulation. The modulation is mainly manifested by positional displacements of O atoms. Barium ions are either eightfold, ninefold or tenfold coordinated in the one-dimensional modulated structure. A significant improvement of the bond-valence sum for both barium positions is achieved by the introduction of the positional modulation. This finding strongly suggests that underbonded barium positions are critically involved in provoking the incommensurate modulation in Ba2TiGe 2O8.

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publishing date
type
Contribution to journal
publication status
published
in
Acta Crystallographica. Section B: Structural Science
volume
59
issue
2
pages
8 pages
publisher
Wiley-Blackwell
external identifiers
  • scopus:2442661839
ISSN
0108-7681
DOI
10.1107/S0108768102021353
language
English
LU publication?
no
id
35c9f5bc-1526-4c9d-8512-60907640c1db
date added to LUP
2019-04-08 15:28:08
date last changed
2022-01-31 18:51:58
@article{35c9f5bc-1526-4c9d-8512-60907640c1db,
  abstract     = {{<p>The incommensurately modulated structure of the fresnoite framework-structure type compound Ba<sub>2</sub>TiGe<sub>2</sub>O<sub>8</sub> has been solved using a (3 + 1)-dimensional superspace approach. The structure is orthorhombic and adopts the superspace group Cmm2(0,β,1/2)s00 with β ≃ 0.635 at room temperature. The refinement was based on neutron powder diffraction data obtained from a powdered single crystal grown by Czochralski pulling. The modulation parameters that were obtained support the idea that frozen-in rigid-unit modes cause the modulation. The modulation is mainly manifested by positional displacements of O atoms. Barium ions are either eightfold, ninefold or tenfold coordinated in the one-dimensional modulated structure. A significant improvement of the bond-valence sum for both barium positions is achieved by the introduction of the positional modulation. This finding strongly suggests that underbonded barium positions are critically involved in provoking the incommensurate modulation in Ba<sub>2</sub>TiGe <sub>2</sub>O<sub>8</sub>.</p>}},
  author       = {{Höche, Thomas and Esmaeilzadeh, Saeid and Uecker, Reinhard and Lidin, Sven and Neumann, Wolfgang}},
  issn         = {{0108-7681}},
  language     = {{eng}},
  month        = {{04}},
  number       = {{2}},
  pages        = {{209--216}},
  publisher    = {{Wiley-Blackwell}},
  series       = {{Acta Crystallographica. Section B: Structural Science}},
  title        = {{(3 + 1)-dimensional structure refinement of the fresnoite framework-structure type compound Ba<sub>2</sub>TiGe<sub>2</sub>O<sub>8</sub>}},
  url          = {{http://dx.doi.org/10.1107/S0108768102021353}},
  doi          = {{10.1107/S0108768102021353}},
  volume       = {{59}},
  year         = {{2003}},
}