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The same is true in a unit cell; no matter how the atoms are arranged, there will be interstitial sites present between the atoms. These sites or holes can be filled with other atoms (interstitial defect). The picture with packed circles is only a 2D representation. In a crystal lattice, the atoms (spheres) would be packed in a 3D arrangement ...
Interstitial atoms (blue) occupy some of the spaces within a lattice of larger atoms (red) In materials science, an interstitial defect is a type of point crystallographic defect where an atom of the same or of a different type, occupies an interstitial site in the crystal structure.
A nearby pair of a vacancy and an interstitial is often called a Frenkel defect or Frenkel pair. This is caused when an ion moves into an interstitial site and creates a vacancy. Due to fundamental limitations of material purification methods, materials are never 100% pure, which by definition induces defects in crystal structure.
In BCC metals, interstitial sites of an unstrained lattice are equally favorable. The interstitial solutes create elastic dipoles. [ 14 ] However, once a strain is applied on the lattice, such as that formed by a dislocation, 1/3 of the sites become more favorable than the other 2/3.
In condensed matter physics and inorganic chemistry, the cation-anion radius ratio can be used to predict the crystal structure of an ionic compound based on the relative size of its atoms. It is defined as the ratio of the ionic radius of the positively charged cation to the ionic radius of the negatively charged anion in a cation-anion compound.
The Wyckoff positions are named after Ralph Wyckoff, an American X-ray crystallographer who authored several books in the field.His 1922 book, The Analytical Expression of the Results of the Theory of Space Groups, [3] contained tables with the positional coordinates, both general and special, permitted by the symmetry elements.
A cation site can be represented by the symbols C or M (for metal), and an anion site can be represented by either an A or X. C corresponds to the electronic charge of the species relative to the site that it occupies. The charge of the species is calculated by the charge on the current site minus the charge on the original site.
Many kink sites are visible along the terrace edge. The rows visible are dimer rows in a 2x1 reconstruction. Figure 3: Ball model representation of a real (atomically rough) crystal surface with steps, kinks, adatoms, and vacancies in a closely packed crystalline material. Adsorbed molecules, substitutional and interstitial atoms are also ...