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The Body centered cubic structure (BCC). It is not a close packed structure. In this each metal atom is at the centre of a cube with 8 nearest neighbors, however the 6 atoms at the centres of the adjacent cubes are only approximately 15% further away so the coordination number can therefore be considered to be 14 when these are on one 4 fold ...
In Hermann–Mauguin notation, space groups are named by a symbol combining the point group identifier with the uppercase letters describing the lattice type.Translations within the lattice in the form of screw axes and glide planes are also noted, giving a complete crystallographic space group.
For face-centered cubic (fcc) and body-centered cubic (bcc) lattices, the primitive lattice vectors are not orthogonal. However, in these cases the Miller indices are conventionally defined relative to the lattice vectors of the cubic supercell and hence are again simply the Cartesian directions .
Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a square base (a by a) and height (c, which is different from a).
The primitive unit cell for the body-centered cubic crystal structure contains several fractions taken from nine atoms (if the particles in the crystal are atoms): one on each corner of the cube and one atom in the center. Because the volume of each of the eight corner atoms is shared between eight adjacent cells, each BCC cell contains the ...
Wigner–Seitz primitive cell for different angle parallelogram lattices. The unique property of a crystal is that its atoms are arranged in a regular three-dimensional array called a lattice . All the properties attributed to crystalline materials stem from this highly ordered structure.
Bravais lattices Example compounds Allowed reflections Forbidden reflections Simple cubic Po Any h, k, ℓ: None Body-centered cubic Fe, W, Ta, Cr h + k + ℓ = even h + k + ℓ = odd Face-centered cubic (FCC) Cu, Al, Ni, NaCl, LiH, PbS h, k, ℓ all odd or all even h, k, ℓ mixed odd and even Diamond FCC Si, Ge All odd, or all even with h + k ...
The Bravais lattices in the hexagonal crystal family can also be described by rhombohedral axes. [4] The unit cell is a rhombohedron (which gives the name for the rhombohedral lattice). This is a unit cell with parameters a = b = c ; α = β = γ ≠ 90°. [ 5 ]