text: Common sphere packings taken on by atomic systems are listed below with their corresponding packing fraction.
  * Hexagonal close-packed (HCP): 0.74
  * Face-centered cubic (FCC): 0.74 (also called cubic close-packed, CCP)
  * Body-centered cubic (BCC): 0.68
  * Simple cubic: 0.52
  * Diamond cubic: 0.34
  The majority of metals take on either the HCP, FCC, or BCC structure.