Packing Efficiency in hcp and ccp Structures
let the unit cell edge length be ‘a’ and face diagonal AC = b.
Let r be the radius of the sphere. So we get
Each unit cell in ccp structure has effectively 4 spheres.
Hence total volume of four spheres is equal to 4 X (4/3)Π r3 and volume of the cube is a3 or (2√2r)3.
Therefore, Packing efficiency = (Volume occupied by four spheres in the unit cell X 100)/( Total volume of the unit cell)
