facecentered

Facecentered describes a cubic lattice arrangement in which lattice points occupy the centers of all faces of a cube in addition to the corner points. The standard term in crystallography is face-centered cubic, often abbreviated as FCC. In the conventional cubic unit cell, there are lattice points at the eight corners (each shared among eight cells) and at the centers of all six faces (each shared between two cells), yielding four atoms per unit cell.

The arrangement is highly efficient for packing: each atom has twelve nearest neighbors, giving a coordination number of 12. The packing density is high, making face-centered cubic structures common among metals. The atoms form a close-packed arrangement along the {111} planes, which gives rise to characteristic slip systems and high ductility.

FCC is one of the 14 Bravais lattices; the conventional cubic cell contains lattice points at the corners and face centers, but the underlying Bravais lattice can be viewed as a cubic lattice with a basis of four atoms. The reciprocal lattice of FCC is body-centered cubic (BCC).

Many elements crystallize in the FCC structure at ambient conditions, including copper, aluminum, silver, gold, nickel, and platinum. Some alloys and compounds also adopt the FCC arrangement. This structure is contrasted with simple cubic, which has points only at the corners, and body-centered cubic, which has a lattice point at the body center in addition to corner points.