Atoms in solid copper and in a dozen other metals adopt the ababab...stacking pattern when they solidify. To understand the sort of crystals they form, consider what happens when we take a cluster of 14 spheres stacked in an ababab...pattern and turn the cluster about 45 digree as shown in Figure 11.9. The atoms form a cube: 8 of the at the 8 corners of the cube and 6 at the centers of each of the 6 faces. Because the atoms are stacked together as closely as possible, this structure is called cubic closest-packed (ccp), and yhe corresponding unit cell is called a face-centered cubic (fcc) unit cell. In the fcc unit cell, the atoms at the other, but they do not touch each along the face diagonal, a line that connects the centers of the atoms at opposite corners of any face of the cube. The edges of the fcc unit cell are all of equal length, and the angle between any two edges is 90 digree