Faculty: Professor Shmuel Mardix
Department of Electrical Engineering
STA: Josh Sisson
Date: 2005

In any crystal, there is a basic arrangement of atoms that is repeated throughout the entire crystal. This periodic arrangement is known as a lattice. The piece contained within the lattice that is repeated over and over is called a unit cell. The smallest and most basic piece that can be repeated over and over to form the lattice is sometimes called a primitive cell instead of a unit cell. The primitive cell contains a few atoms in a specific arrangement. The specific arrangement is defined by a lattices cubic structure.
This page attempts to help the viewer visualize different primitive cells for the most common cubic structures. These primitive cell types include the simple cubic (SC), the body-centered cubic (BCC), the face-centered cubic (FCC), and the diamond primitive cell types.

Click to view crystal animation Click and drag on the animation to move the crystal.

Quicktime player is needed to view the above animation.

Each cell type includes a description to learn more about each cell structure.

The structure shown here, the face-centered cubic, has an atom located at each of the 8 corners of the unit cell, and additional atoms centered on each of the 6 faces of the unit cell. The packing efficiency is about 74%, and is the maximum packing efficiency for atoms of the same radii. Calcium will form into this structure.