Search results
Results from the WOW.Com Content Network
2×2×2 unit cells of a diamond cubic lattice. In three-dimensional space there are 14 Bravais lattices. These are obtained by combining one of the seven lattice systems with one of the centering types. The centering types identify the locations of the lattice points in the unit cell as follows:
The direct lattice or real lattice is a periodic function in physical space, such as a crystal system (usually a Bravais lattice). The reciprocal lattice exists in the mathematical space of spatial frequencies, known as reciprocal space or k space, which is the dual of physical space considered as a vector space, and the reciprocal lattice is ...
The translation vectors define the nodes of Bravais lattice. The lengths of principal axes/edges, of unit cell and angles between them are lattice constants, also called lattice parameters or cell parameters. The symmetry properties of crystal are described by the concept of space groups. [1]
In geometry and crystallography, a Bravais lattice is a category of translative symmetry groups (also known as lattices) in three directions. Such symmetry groups consist of translations by vectors of the form R = n 1 a 1 + n 2 a 2 + n 3 a 3, where n 1, n 2, and n 3 are integers and a 1, a 2, and a 3 are three non-coplanar vectors, called ...
For the base-centered monoclinic lattice, the primitive cell has the shape of an oblique rhombic prism; [1] it can be constructed because the two-dimensional centered rectangular base layer can also be described with primitive rhombic axes.
In either case, one needs to choose the three lattice vectors a 1, a 2, and a 3 that define the unit cell (note that the conventional unit cell may be larger than the primitive cell of the Bravais lattice, as the examples below illustrate). Given these, the three primitive reciprocal lattice vectors are also determined (denoted b 1, b 2, and b 3).
The face-centered cubic lattice (cF) has lattice points on the faces of the cube, that each gives exactly one half contribution, in addition to the corner lattice points, giving a total of four lattice points per unit cell (1 ⁄ 8 × 8 from the corners plus 1 ⁄ 2 × 6 from the faces).
For example, 2 1 is a 180° (twofold) rotation followed by a translation of 1 / 2 of the lattice vector. 3 1 is a 120° (threefold) rotation followed by a translation of 1 / 3 of the lattice vector. The possible screw axes are: 2 1, 3 1, 3 2, 4 1, 4 2, 4 3, 6 1, 6 2, 6 3, 6 4, and 6 5.