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Effects of the choice of different ionization level for scattering curves and correction for small preferred orientation in Rietveld refinement: the MgAl 2 O 4 test case
Author(s) -
Ballirano Paolo
Publication year - 2003
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/s0021889803010410
Subject(s) - rietveld refinement , scattering , orientation (vector space) , ionization , spherical harmonics , harmonics , chemistry , computational physics , materials science , mathematics , physics , crystal structure , crystallography , geometry , optics , mathematical analysis , ion , quantum mechanics , voltage
The effects of the choice of oxygen scattering curves with different ionization levels and of the number of spherical harmonics terms used to correct for preferred orientation are discussed in the case of the Rietveld refinement of MgAl 2 O 4 spinel. Results indicate that Rietveld refinements, and not only single‐crystal analyses, are influenced by the choice of the scattering curves, at least in the case of very simple ionic structures. Improvements are observed both in agreement indices and in displacement parameter modelling by the use of an almost fully ionized model. On the contrary, the choice of the order of spherical harmonics prevalently affects the fractional u coordinate.