Question

How know that in crystal lattice structure only some variation is possible?
For example,
In Cubic - FCC, primitive,BCC found But In tetragonal - only primitive and BCC found
How to know that?​

Answer 1

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In general, crystals consist of solid materials where its atoms tend to form regular geometric patterns. The smallest group of particles in the material are unit cells. These cells help define the symmetry and structure of the crystal lattice, which is built up by unit cells along the axes of the crystal.