Determination of Point Group - Practical Electron Microscopy and Database - - An Online Book - |
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Microanalysis | EM Book https://www.globalsino.com/EM/ | ||||||||||||||||||||||||
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A crystal of a specific Laue symmetry or point group may give rise to different diffraction groups at different zone-axis orientations, and thus there may be several possible space groups. The choice may be reduced through use of "systematic extinctions" in diffractions indicating glide planes or screw axes. Even though some techniques can be used to determine the space groups and point group of crystals, the determination procedure is usally not simple. The diffuculties can be significantly reduced if we know some relavent characteristics of the materials such as listed in Table 1625. However, if one wants to be an expert on electron crystallography, he should get familiar with all the methods for point group determination. Table 1625. Materials’ characteristics related to their space groups and point groups.
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