Crystal lattices and unit cells
Solid State · Chemistry
Study notes
A cubic unit cell has edge 400 pm. How many unit cells are in 1 cm³ of the crystal? Step 1: Cell volume = (400 × 10⁻¹⁰ cm)³ = (4 × 10⁻⁸)³ = 6.4 × 10⁻²³ cm³. Step 2: Number = 1 / 6.4 × 10⁻²³ = 1.56 × 10²² cells. Step 3: Each cell is sub-nanometre — crystals pack ~10²² unit cells per cm³. The unit cell is the crystal's 'brick'; the lattice is the wall.