ALL MOLECULAR GRAPHICS: METALS: CRYSTAL STRUCTURE: CLOSE PACKING: hexagonal close packing
(above) atoms arranged in a hexagonal close packing pattern
METALLIC STRUCTURE: the atoms in metals are arranged in several ways. Generally, they pack together very tightly. The variant shown here is called hexagonal close packing (the other close packing variant is called face centred cubic pattern or cubic close packing). In HCP the metal atoms are arranged in closely packed hexagonal layers and alternate layers are in line with each other. The translucent purple volume illustrates six atoms in the top layer (a hexagon), three atoms in the middle and six atoms in the third layer. These atoms all belong to a unit cell (illustrated as a dark pink solid structure whose vertices lie at the centres of the atoms mentioned). A vast array of such unit cells makes up the crystal of the metal.
Image is 500 pixels across, the originals are 4096 pixels across.