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I'm studying basics of Solid State Chemistry from this source.

So 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. OK so far so good.

Later on there was the topic of Close packing and Structure of Metallic Crystals and we are told about hcp /fcc types of structures.

Problems:

  • Why do we remain silent about the unit cells and crystal system in this context? It seems like a huge disconnect.

  • Is there any relation between the Hexagonal Unit cell and hexagonal close packing?

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    $\begingroup$ Certainly many books are not silent on unit cells, how to construct them, and the difference between customary unit cells and ones that reflect the full unit cell symmetry (such as Wigner-Seitz unit cells). So I'm quite unclear about just what you are asking. $\endgroup$ – Jon Custer Sep 25 '17 at 18:19
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We do not remain silent about the unit cells in this context. The hexagonal close packed structure is called so because it has hexagonal unit cell, and the other one is called fcc precisely because its unit cell is face-centered cubic.

fcc cell hcp cell (source)

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