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?

Answer 1

Answer:

In crystal structure close packing is define as space efficient arrangement of constituent particles to form a crystal lattice.

Explanation:

closest packing

In crystal structure close packing is define as space efficient arrangement of constituent particles to form a crystal lattice.

Difference between hexagonal closest packing and cubic closest packing

In cubic closest packing arrangement, each sphere is surrounded by 12 other spheres on the other hand in case of hexagonal close packing, layers of spheres are packed so that spheres in alternating layers overlie one another.

unit cell for each closest packing arrangement

The hexagonal closest packed arrangement has a coordination number of 12 and it consists of 6 atoms per unit cell. The face centered cubic lattice has a coordination number of 12 and it consists of 4 atoms per unit cell. In case of body centered cubic crystal the coordination number is 8 and it consists of 2 atoms per unit cell.