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Superspace description of the crystal structures of Ca\sb \it n(Nb,Ti)\sb \it nO\sb 3\it n+2 (\it n = 5 and 6)

Title data

Guevarra, Jonathan ; Schönleber, Andreas ; van Smaalen, Sander ; Lichtenberg, Frank:
Superspace description of the crystal structures of Ca\sb \it n(Nb,Ti)\sb \it nO\sb 3\it n+2 (\it n = 5 and 6).
In: Acta Crystallographica Section B. Vol. 63 (2007) Issue 2 . - pp. 183-189.
ISSN 2052-5206
DOI: https://doi.org/10.1107/S0108768107002340

Abstract in another language

The crystal structures of two members of the homologous series Ca\sb \it n(Nb,Ti)\sb \it nO\sb 3\it n+2, with \it n = 5 and 6, are presented within the superspace formalism. A common (3+1)-dimensional superspace model is used to describe the crystal structures of both compositions within a particular homologous series, where the primary modulation wavevector and the width of the atomic domains vary systematically with composition. The two crystal structures are characterized as commensurately modulated structures consisting of discontinuous atomic domains described by occupational crenel functions. The displacive modulation functions for the two compounds exhibit similarities, but they also show that the idea of a unified superspace model does not extend toward the precise atomic positions. For \it n = 6, the centrosymmetric (3+1)-dimensional superspace symmetry provides a natural explanation for the pseudo-symmetries that are present in the non-centrosymmetric (three-dimensional) superstructure of this compound. The efficiency of the superspace approach is demonstrated by structure refinements in (3+1)-dimensional superspace and by comparing these results with the refinements in their three-dimensional superstructures.

Further data

Item Type: Article in a journal
Refereed: Yes
Keywords: superspace description; homologous series; commensurately modulated structures
Institutions of the University: Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences > Chair Crystallography > Chair Crystallography - Univ.-Prof. Dr. Sander van Smaalen
Faculties
Faculties > Faculty of Mathematics, Physics und Computer Science
Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences
Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences > Chair Crystallography
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 530 Physics
Date Deposited: 26 Feb 2016 07:53
Last Modified: 26 Feb 2016 07:53
URI: https://eref.uni-bayreuth.de/id/eprint/31185