Electron microscopy
Long Range Ordering (LRO) in Materials
- Practical Electron Microscopy and Database -
- An Online Book -
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This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.


Atomic structure ordering in materials can be categorized by::
        i) Short range ordering (SRO).
        ii) Medium range ordering (MRO).
        iii) Long range ordering (LRO).

Table 3102 summarizes the some basic differences between crystals, glasses, and liquids.

Table 3102. Some basic differences between crystals, glasses, and liquids.

Basic differences
Long-range ordering
Short-range ordering
No ordering to short-range ordering

The LRO structural organization is normally characteristic for crystalline materials, in which the positions of the atoms are arranged accurately throughout the whole crystal. A electron diffraction pattern of an amorphous specimen is typically a halo feature, while a diffraction pattern of a polycrystalline specimen shows well defined sharp Debye-Scherrer rings, indicating the presence of LRO in the specimen. In other words, different from Bragg peaks, local/temporal deviation from the long-range ordered structure causes diffuse scattering intensities in the diffraction pattern.



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