Bimodal distribution

The parallelogram is the general primitive cell for the plane.

A parallelepiped is a general primitive cell for 3-dimensional space.

A primitive cell is a unit cell built on the primitive basis of the direct lattice, namely a crystallographic basis of the vector lattice L such that every lattice vector t of L may be obtained as an integral linear combination of the basis vectors, a, b, c.

Used predominantly in geometry, solid state physics, and mineralogy, particularly in describing crystal structure, a primitive cell is a minimum volume cell corresponding to a single lattice point of a structure with translational symmetry in 2 dimensions, 3 dimensions, or other dimensions. A lattice can be characterized by the geometry of its primitive cell.

The primitive cell is a fundamental domain with respect to translational symmetry only. In the case of additional symmetries a fundamental domain is smaller.

A crystal can be categorized by its lattice and the atoms that lie in a primitive cell (the basis). A cell will fill all the lattice space without leaving gaps by repetition of crystal translation operations.

Primitive translation vectors are used to define a crystal translation vector, $\overrightarrow{T}$, and also gives a lattice cell of smallest volume for a particular lattice. The lattice and translation vectors ${\overrightarrow{a}}_1$, ${\overrightarrow{a}}_2$, and ${\overrightarrow{a}}_3$ are primitive if the atoms look the same from any lattice points using integers $u_1$, $u_2$, and $u_3$.

$\overrightarrow{T}=u_1{\overrightarrow{a}}_1+u_2{\overrightarrow{a}}_2+u_3{\overrightarrow{a}}_3$

The primitive cell is defined by the primitive axes (vectors) ${\overrightarrow{a}}_1$, ${\overrightarrow{a}}_2$, and ${\overrightarrow{a}}_3$. The volume, $V_p$, of the primitive cell is given by the parallelepiped from the above axes as

$V_p=|{\overrightarrow{a}}_1\cdot ({\overrightarrow{a}}_2\times {\overrightarrow{a}}_3)|.$

See also

• Bravais lattice
• Wallpaper group
• Space group