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Element and its Crystal Structure

FCC and BCC are two of the most iconic crystal structures. Nearly all elements have FCC,

BCC, or HCP structures. The most direct difference between FCC and BCC crystals is in the
atomic arrangements. The face-centered cubic structure has an atom at all 8 corner positions,
and at the center of all 6 faces. The body-centered cubic structure has an atom at all 8 corner
positions, and another one at the center of the cube. HCP in a different case which HCP atom
arrangement is in hexagonal not cubic. Figure 2.24 below show example of elements and their

crystal structures.

Figure 2.24: Crystal structure of elements at room temperature

Atomic Packing Factor (APF)

Atomic Packing Factor (APF) tells what percent of an object is made of atoms versus

empty space. Can think of this as a volume density, or as an indication of how tightly-packed
the atoms are.

For quick reference, Table 2.7below of atomic packing factor (APF) values
for common crystal structures.

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