# What is the difference between primitive Hexagonal unit cell and Hexagonal closed packing HCP [duplicate]

There are 14 types of Bravais crystal lattices (Primitive + Centered) in 3D. Every solid in this universe is made by the unit cells of these lattices.

With the help of these Bravais lattice can HCP be formed?. Is there any relation between Hexagonal unit cell and Hexagonal close packing As we see that Hexagonal unit cell exists only in primitive AAA form then how can HCP ABA be formed from it .

Primitive Hexagonal unit cell

Hexagonal closed packing HCP

If there is a clear distinction then Should HCP also be placed among 14 Bravais lattice.

With the help of these Bravais lattice can HCP be formed?

Yes. One choice of unit cell for HCP is a primitive hexagonal cell with two atoms per unit cell. If you place the first atom on the origin, the second will be at (1/3 2/3 1/2). Here is a 3D view of the situation and some more information: http://lampx.tugraz.at/~hadley/ss1/crystalstructure/structures/hcp/hcp.php

Should HCP also be placed among 14 Bravais lattice?

No, because it is already in there, just hiding a bit. If you look further into it, the space group is #194, P$$6_3$$/mmc, see http://img.chem.ucl.ac.uk/sgp/large/194az1.htm