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Structural disorder in microcrystalline MgCl 2
Author(s) -
Giunchi G.,
Allegra G.
Publication year - 1984
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/s0021889884011250
Subject(s) - diffraction , spectral line , basis (linear algebra) , materials science , crystal (programming language) , microcrystalline , crystallography , condensed matter physics , type (biology) , physics , chemistry , mathematics , geometry , optics , geology , quantum mechanics , paleontology , computer science , programming language
Structural disorder in severely ground MgCl 2 is interpreted on the basis of a Bernoullian model with four parameters, specifying both the size and the statistical sequence of the layers; their choice completely dictates the intrinsic shape of all the X‐ray diffraction lines. The X‐ray powder spectra are reasonably well reproduced over a wide range of Bragg distances (~1.7 < d < ~9 Å) for samples with various degrees of disorder. Practical criteria are given to derive the statistical parameters from the X‐ray spectra. Average crystal thickness as small as 20 Å across the layers is observed. From the usual structure with cubic packing in the Cl atoms, with increasing disorder at first the probabilities of cubic and hexagonal‐like interlayer shifts ( P cub and P hex ) tend to become equal; the ultimate degree of disorder also involves ± 60° rotations between adjacent layers, with about the same probability as P cub and P hex .