Question

What is closest packing? What is the difference between hexagonal closest packing and cubic closest packing? What is the unit cell for each closest packing arrangement?

Short answer

The third layer of cubic closest packing covers all octahedral holes and is not aligned with layer A, and the structure will start repeating from the fourth layer. In hexagonal closest packing, each layer is aligned in such a way that it fits in the holes formed in the previous layer. The unit cell for CCP is 4 and for HCP is 8 .

Step-by-step solution

Define the closest packing.

Closest packing is the highly effective configuration of atomic spheres that can take within a unit cell.

The packing is most tightly packed or the space-effective configuration of crystal structures.

Determine the difference between the hexagonal closest packing and the cubic closest packing.

In cubic closest packing, the third layer of structure covers all octahedral holes and is not aligned with layer A , and the structure will start repeating from the fourth layer

In hexagonal closest packing, each layer of the structure is aligned so that it fits in the holes formed in the previous layer.

Determine the unit cell for each closest packing arrangement.

The cubic closest packing structure has 4 spheres, while the hexagonal closest packing has 8 spheres per unit cell.