Hand-thrown Pottery by Emily Asenath-Smith, PhD
Symmetry
Symmetry is everywhere; in nature and in the creations of human kind. It is pleasing to the eye and can puzzle the mind when exploring the relationships within symmetry objects. Take for example a cube, which contains a whole variety of different symmetry relationships. While the cube is often thought to be unique for the symmetry of its square cross section, it is actually the three-fold rotational symmetry at each corner that makes it unique. Next time you have a cube handy, look down one diagonal corner and rotate to see the three-fold rotational axis.
Symmetry is very important to the study of materials as symmetry defines the properties of crystals. Symmetry that we observe with our eyes often stems from the symmetric arrangements of the constituent elements that compose the material. Consider first, the simplest structural arrangement for a solid material: the cube. Many metals exist with cubic crystal structures.
The unit cell is the smallest unit from which crystals and minerals are put together. When the unit cell is translated in all directions, one arrives at the crystal lattice. Keep propagating the unit cell and eventually you arrive at the macroscale form of a crystal, which has a habit defined by the planes of atoms that make up the material.
Metals have the simplest crystal structures. Think of how you could stack ping pong balls in a box and you can visualize the cubic and hexagonal motifs that result. Below is shown a unit cell of a cubic metal. The unit cell is a cube with one metal atom at each corner and one in the center of the cube body.
