@@ -412,6 +412,13 @@ If a crystal is symmetric under $90^\circ$ rotations, then $(100)$, $(010)$ and
## Exercises
### Quick warm-up exercises
1. Draw a unit cell of an FCC, a BCC, and a triangular lattice. Are the unit cells you drew primitive?
2. How many lattice points are there in a primitive unit cell?
3. Suppose you found the primitive unit cell of a diatomic crystal. How many basis vectors do you minimally need to describe the crystal? Can some diatomic crystals require more basis vectors?
### Exercise 1: Diatomic crystal
Consider the following two-dimensional diatomic crystal:
