The structure of a hexagonal close-packed (HCP) metal consists of close-packed planes of atoms in an ..ABAB.. orientation. The figure shows the first layer in a HCP structure with an orientation arbitrarily called the A orientation.

All atoms in planes labeled with an "A" have the same environment. Thus a lattice point can be placed at the center of each atom in planes labeled "A". A hexagonal unit cell can be selected as shown on the next page.

Click the links on the right to show a few layers of a HCP structure.