The small wavelengths used in electron-diffraction experiments and the thinness of the crystals necessary for the transmission of the electron beam combine to require a somewhat different diffraction geometry for the interpretation of electron-diffraction patterns than is used in the interpretation of X-ray diffraction patterns. This geometry, based on the reciprocal lattice concept and geometrical construction of Ewald, needed for the interpretation. of transmission electron-diffraction single-crystal patterns is here reviewed.
Transmission electron-diffraction single-crystal patterns of two monoclinic substances, colemanite [CaB3O3(OH)3•H2O] and potassium chlorate (KC103), are examined and the .theory necessary for their interpretation is given in detail. The study of these patterns furnishes a basis for the interpretation of single-crystal patterns of materials belonging to any crystal system. It is shown that useful unit-cell data, accurate to a few tenths of a percent, can be obtained from the patterns of colemanite and KClO3. A method of evaluating unit-cell data from measurements of such single-crystal patterns is given.
The transmission electron-diffraction powder pattern obtained from an oriented aggregate of thin crystals gives the same unit-cell data as are given by the electron-diffraction single-crystal pattern obtained from one crystal of the aggregate., A graphical method is given for precisely evaluating unit-cell constants from measurements of such a powder pattern.
Additional publication details
|Publication Subtype||USGS Numbered Series|
|Title||Mineralogical applications of electron diffraction. 1. Theory and techniques|
|Series title||Trace Elements Investigations|
|Publisher||U.S. Geological Survey|