Oktaedrikerros

Oktaedrikerros, also known as octahedral void, is a term used in crystallography and solid-state chemistry. It refers to a specific type of interstitial site within a crystal lattice structure. These sites are located between atoms in a close-packed arrangement, such as face-centered cubic (FCC) or hexagonal close-packed (HCP) structures. An octahedral void is so named because its surrounding atoms, when viewed in isolation, form the vertices of an octahedron.

In a close-packed structure, there are typically two types of interstitial voids: tetrahedral and octahedral. Octahedral voids are larger than tetrahedral voids and are typically found in greater numbers. Specifically, in an FCC lattice, there is one octahedral void per lattice point, and these voids are located at the center of each unit cell and at the midpoint of each edge. In an HCP lattice, octahedral voids are also present, located at the center of the unit cell and at specific positions within the structure.

These interstitial sites can be occupied by smaller atoms or ions, forming alloys or interstitial compounds. The presence and location of octahedral voids play a crucial role in determining the physical and chemical properties of crystalline materials, including their density, electrical conductivity, and reactivity. For example, in many metal hydrides and carbides, hydrogen or carbon atoms occupy these octahedral sites. The size and geometry of the octahedral void influence which solute atoms can be accommodated.