What is a metallic crystal lattice and the “unit cell”?
I’ll answer these in reverse order: A unit cell is the smallest complete crystal of the metal. For example, room temperature iron forms a body-centered cubic (BCC) unit cell (a cube with one iron atom at each corner and one in the very center of the cube). Now imagine that you add more iron atoms to the single BCC unit cell to build out rows and layers of repeating unit cells in all three dimensions. The result would be a bigger cube made up of many small cubes (unit cells). This larger structure is a crystal of iron, and the repeating 3-D arrangement that makes it up is the crystal lattice. There are other shapes for unit cells, but the idea is the same.
