In
mineralogy and
crystallography,
crystal structure is a unique arrangement of
atoms or
molecules in a
crystalline
liquid or
solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry. Patterns are located upon the points of a
lattice, which is an array of points repeating periodically in three dimensions. The points can be thought of as forming identical tiny boxes, called unit cells, that fill the space of the lattice. The lengths of the edges of a unit cell and the angles between them are called the
lattice parameters. The
symmetry properties of the crystal are embodied in its
space group.
A crystal's structure and symmetry play a role in determining many of its physical properties, such as
cleavage,
electronic band structure, and
optical transparency.