Example 4 : Calculate the density of Si from the lattice constant, atomic weight, and Avogadro's number. Recall: Avogadro's number (6.02 × 10²³ ) is the number of molecules/atoms in a gram molecular weight of a substance. Lattice constant = a = 5.43 x 10^-8 cm

How many Si atoms in the diamond cell?

8 corner atoms x (1/8) = 1

6 face atoms x (1/2) = 3

+ 4 interior atoms = 4

Total 8 atoms/unit cell