FCCStruktur

FCCstruktur, or cubic close-packed structure, is a common crystal arrangement used to describe how atoms are organized in many metals. In a conventional face-centered cubic unit cell, atoms are located at all eight corners and at the centers of all six faces. Although there are 14 lattice-atom positions in the cell, each corner atom is shared by eight cells and each face-centered atom by two, resulting in four atoms effectively per unit cell.

Key geometric properties include a coordination number of 12 and a nearest-neighbor distance of a/√2, where a is the lattice constant. The structure achieves a packing efficiency of about 74%, making it one of the densest achievable arrangements for spherical atoms. The close-packed layers follow an ABCABC… stacking sequence along the [111] direction.

FCC lattices exhibit numerous slip systems, specifically the {111} planes with <110> directions, which contributes to high ductility and formability in metals. This makes FCC metals generally more capable of plastic deformation before fracture compared with other crystal types.

Examples of materials with an FCC structure include copper, aluminum, silver, gold, nickel, and platinum, among others. The FCC arrangement is often contrasted with body-centered cubic (BCC) and hexagonal close-packed (HCP) structures. Among cubic lattices, FCC and HCP represent the two close-packed arrangements, both delivering high packing density and distinct mechanical properties due to their different stacking and slip characteristics.

In summary, the FCC structure is defined by face-centered atoms within a cubic cell, four atoms per cell, 12-fold coordination, and high ductility, making it a fundamental concept in crystallography and materials science.