There are two types of spaces in close-packed lattices. The spaces between the spheres are also referred to as sites because, as seen in the module on Ionic Solids, these may be occupied in lattices of substances having two different atoms or ions.
Octahedral sites are surrounded by six spheres.
These are located at the center of each edge and the centre of the face-centred unit cell.
Roll over the image at the right to see the octahedral site at the centre of the face-centred cubic unit cell.
Tetrahedral sites are surrounded by four spheres.
In the face-centred cubic unit cell, the tetrahedral sites are under (or above) each corner on the body diagonal.
The spheres surrounding one tetrahedral sites are highlighted at the right.
There are eight tetrahedral sites inside the unit cell for a face-centred cubic lattice.
These are located at the center of each edge and the centre of the face-centred unit cell.
Roll over the image at the right to see the octahedral site at the centre of the face-centred cubic unit cell.
Tetrahedral sites are surrounded by four spheres.
In the face-centred cubic unit cell, the tetrahedral sites are under (or above) each corner on the body diagonal.
The spheres surrounding one tetrahedral sites are highlighted at the right.
There are eight tetrahedral sites inside the unit cell for a face-centred cubic lattice.
There is one type of site in a simple cubic lattice. It is referred to as a cubic site and is located at the centre of the unit cell.
Cubic sites are surrounded by eight spheres.
Cubic sites are surrounded by eight spheres.