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The dislocation model of strain anisotropy in whole powder‐pattern fitting: the case of an Li–Mn cubic spinel
Author(s) -
Ungár T.,
Leoni M.,
Scardi P.
Publication year - 1999
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889898012710
Subject(s) - anisotropy , materials science , dislocation , spinel , crystallography , condensed matter physics , diffraction , synchrotron , rietveld refinement , neutron diffraction , powder diffraction , optics , physics , composite material , metallurgy , chemistry
Anisotropic strain broadening in X‐ray or neutron powder diffraction can cause severe difficulties in whole powder‐pattern fitting and Rietveld structure refinement. Several phenomenological models have been proposed to deal with this problem. These, however, lack physically sound bases. In the present work the dislocation‐based model of strain anisotropy is applied in the Fourier formalism of profile fitting. It is shown that the anisotropic contrast of dislocations can fully account for strain anisotropy. A few physically sound parameters, namely the average dislocation density, the average coherent domain size, the dislocation arrangement parameter and the dislocation contrast factors, enable a perfect profile fitting to the powder pattern of a cubic Li–Mn spinel obtained at the Daresbury synchrotron storage ring.