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An example is the Stone Wales defect in nanotubes, which consists of two adjacent 5-membered and two 7-membered atom rings. Schematic illustration of defects in a compound solid, using GaAs as an example. Amorphous solids may contain defects. These are naturally somewhat hard to define, but sometimes their nature can be quite easily understood.
If several twin crystal parts are aligned by the same twin law they are referred to as multiple or repeated twins. If these multiple twins are aligned in parallel they are called polysynthetic twins. When the multiple twins are not parallel they are cyclic twins. Albite, calcite, and pyrite often show polysynthetic twinning.
Among the grain boundaries, it is known that the twin boundaries, a special type of low-energy grain boundary has lower interaction energy with dislocation leading to much smaller saturation size of the grain. [13] The cryogenic dynamic plastic deformation creates higher fraction of the twin boundaries compared to the severe plastic deformation.
Low-angle boundaries, where the distortion is entirely accommodated by dislocations, are Σ1. Some other low-Σ boundaries have special properties, especially when the boundary plane is one that contains a high density of coincident sites. Examples include coherent twin boundaries (e.g., Σ3) and high-mobility boundaries in FCC materials (e.g ...
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For example, in an ordered AB alloy, if an A atom occupies the site usually occupied by a B atom, a type of crystallographic point defect called an antisite defect is formed. If an entire region of the crystal is translated such that every atom in a region of the plane of atoms sits on its antisite, an antiphase domain is formed.
Surface of a nanotwinned copper film with highlighted Σ3 and low angle grain boundaries as imaged by EBSD. Image adapted from Zhao et al. [1] A nanostructured film is a film resulting from engineering of nanoscale features, such as dislocations, grain boundaries, defects, or twinning.
The original use of the term "boundary-work" for these sorts of issues has been attributed to Thomas F. Gieryn, [2] a sociologist, who initially used it to discuss the problem of demarcation, the philosophical difficulty of coming up with a rigorous delineation between what is "science" and what is "non-science". [3] Gieryn defined boundary ...