The crystal structure is cubic, meaning the unit cell is a cube.
The edge length of the unit cell is given as \(a = 0.
4\) nm.
The volume (\(V\)) of a cube is calculated as the edge length cubed:
$$ V = a^3 $$
Substitute the given edge length:
$$ V = (0.
4 \, \text{nm})^3 $$
$$ V = 0.
4 \times 0.
4 \times 0.
4 \, \text{nm}^3 $$
$$ V = 0.
16 \times 0.
4 \, \text{nm}^3 $$
$$ V = 0.
064 \, \text{nm}^3 $$
The volume of the unit cell is 0.
064 nm\(^3\).
Option 3 is incorrect due to the unit (cm\(^3\)).