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Optical transforms of disordered systems containing symmetry‐related scattering sites
Author(s) -
Welberry T. R.,
Withers R. L.
Publication year - 1990
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/s002188989000379x
Subject(s) - reciprocal lattice , scattering , diffraction , symmetry (geometry) , crystallography , space (punctuation) , molecule , distribution (mathematics) , molecular physics , crystal (programming language) , chemistry , condensed matter physics , materials science , physics , optics , geometry , mathematics , quantum mechanics , mathematical analysis , linguistics , philosophy , computer science , programming language
A previously described method of synthesizing a real‐space distribution of scattering points which will give rise to virtually any required diffraction pattern has been extended to include the possibility of multiple symmetry‐related sites per unit cell. The distribution may be used in the form of an optical diffraction screen to give an immediate visual check on both the real‐space and reciprocal‐space distributions. The method has been applied successfully to two examples which exhibit strong diffuse X‐ray scattering effects: a molecular crystal sample, 1,3‐dibromo‐2,5‐diethyl‐4,6‐dimethylbenzene (BEMB2), in which disorder occurs because the molecule can take up two different orientations in any given molecular site, and a mineral mullite, Al 2 (Al 2 + 2 x Si 2 − 2 x )O 10 − x ⊗ x , where disorder diffuse scattering occurs as a result of the oxygen vacancies ⊗ and the accompanying cation displacements.