Premium
An auxiliary method of indexing electron diffraction patterns by means of gnomonic projections
Author(s) -
Borges F. S.
Publication year - 1983
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/s0021889883009966
Subject(s) - diffraction , electron diffraction , orientation (vector space) , planar , stacking , spurious relationship , lattice (music) , projection (relational algebra) , optics , materials science , physics , crystallography , geometry , mathematics , chemistry , computer science , algorithm , nuclear magnetic resonance , computer graphics (images) , statistics , acoustics
A method is described which eliminates most – if not all – spurious solutions usually obtained when indexing an electron diffraction pattern from a substance having a structure with low symmetry. The proposed method is applicable when the diffraction pattern includes non‐zero Laue zones, or when crystallographic planar features are recognized in the contrast images of the areas from which the diffraction patterns were taken. In the first situation, the tangential component of the stacking vector of reciprocal‐lattice planes, normal to each beam direction calculated by the computer for a given diffraction pattern, is determined by means of gnomonic projections, and then compared with the one derived from the observed Laue zones. In the second situation, the trace orientation of a known planar feature observed is compared with those that can be drawn on the gnomonic projections. Alternatively, if a selected‐area diffraction pattern has already been indexed, a presumed crystallographic orientation of a planar feature can be checked on a gnomonic projection.