Question

Calculate packing efficiency in ccp structure.

Answer 1

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)



Answer 2

For ccp structure

packing efficiency = volume occupied by four spheres in the unit cell / total volume of the unit cell  × 100%