Crystal structure

Crystal structure is the ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter.

The smallest group of particles in the material that constitutes this repeating pattern is the unit cell of the structure. The unit cell completely reflects the symmetry and structure of the entire crystal, which is built up by repetitive translation of the unit cell along its principal axes. The translation vectors define a parallelpiped, the shape of which is determined by the magnitudes of the vectors and the angles between them.

Types of Crystal Structures

There are many types of crystal structures in nature, such as body-centered cubic (BCC), face-centered cubic (FCC), and hexagonal close-packed (HCP). These structures are determined by factors such as the size and number of atoms in the unit cell and the conditions under which the material was formed.

Body-centered cubic (BCC)

In a BCC arrangement of atoms, the unit cell consists of eight atoms at the corners of a cube and one atom at the center of the cube. It is referred to as "body-centered" because the central atom is located at the body center of the unit cell.

Face-centered cubic (FCC)

In an FCC arrangement, the unit cell consists of eight atoms at the corners of a cube and one atom centered on each of the cube's six faces. It is referred to as "face-centered" because the additional atoms are located at the center of each face of the unit cell.

Hexagonal close-packed (HCP)

In an HCP arrangement, the unit cell consists of 12 atoms that form a regular hexagon around a central atom. With an additional atom below and above the central atom, the unit cell contains a total of 14 atoms.

See Also

• Crystallography
• Crystal lattice
• Unit cell

References

Crystal structure Resources
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