The simple cubic unit cell is delineated by eight atoms, which mark the actual cube. These are corner atoms, so each one only contributes one eighth of an atom to the unit cell, thus giving us only one net atom.
Click here to view the lattice
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| Simple Cubic The simple cubic unit cell is delineated by eight atoms, which mark the actual cube. These are corner atoms, so each one only contributes one eighth of an atom to the unit cell, thus giving us only one net atom. Click here to view the lattice |
| Body Centered Cubic This unit cell uses nine atoms, eight of which are corner atoms (forming the cube) and one more in the center of the cube. The corners contribute only one net atom and the center atom contributes another for a total of two net atoms. Please, notice that the corner atoms are not touching one another. Instead, the atoms touch through the center atom along the diagonal of the cube. Since the center atom is in contact with eight other atoms, we say that it has a coordination number of eight. Click here to view the lattice |
| Face Centered Cubic This unit cell uses 14 atoms, eight of which are corner atoms (forming the cube) with the other six in the center of each of the faces. Since the face atoms are shared by two cubes, they only contribute three net atoms to the unit cell. These three atoms plus the one from the corners yield the observed four net atoms in the unit cell. Please, notice that once more, the corner atoms do not touch one another, touching instead through the diagonal of the face. Look at the structure carefully and corroborate that we have a coordination number of 12. Click here to view the lattice |
