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Large‐angle convergent‐beam electron diffraction; a simple technique for the study of modulated structures with application to V 2 D
Author(s) -
Taftø J.,
Metzger T. H.
Publication year - 1985
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/s0021889885009918
Subject(s) - monoclinic crystal system , diffraction , electron diffraction , optics , bragg's law , reciprocal lattice , electron , diffraction topography , lattice (music) , gas electron diffraction , cathode ray , selected area diffraction , materials science , physics , reflection high energy electron diffraction , crystallography , crystal structure , chemistry , quantum mechanics , acoustics
With a highly convergent electron beam entering a small crystal area, the Bragg condition may be fulfilled simultaneously for many diffraction orders along a reciprocal‐lattice direction, and reflections with (sin θ )/ λ > 2 Å −1 are accessible. Considerations based on the dynamical theory of electron diffraction suggest that for Bragg reflections with (sin θ )/ λ > 1 Å −1 , 100 keV electrons can be treated quasi‐kinematically when the crystal thickness is less than 1000 Å, and this is supported by experiments. This simple approach has been used to determine the D‐induced static displacement modulation δ of V along the a axis (monoclinic indexing) in the β phase of V 2 D. From visual inspection of the Bragg intensities for large diffraction orders, up to (sin θ )/ λ = 2.35 Å −1 , it is concluded that δ = 0.070 (5) Å.