Cubic close-packed crystal structure. Computer artwork of a cubic close-packed, or face-centred cubic, crystal lattice, a common arrangement of atoms in solids. This is a type of lattice in which a layer of atoms (spheres) lies in the holes between atoms in the layer below it, and the layer below that lies beneath the holes in both the layers. It is as tightly packed together as spheres can be, filling 74% of the available space. This arrangement of atoms is favoured by several metals, including gold and silver.