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| A
unit cell is the smallest structural unit that exhibits the full structure
of a crystal. The crystal structure has two components, a Bravais lattice
and the basis (atom group) that is placed with identical orientation on
each lattice point.
The
Bravais lattice (top diagram) is defined in terms of the primitive translation
vectors, a, b, c, and the angles between them,
a, b, g, and yields
14 different lattice structures that can be divided into 7 groups of the
same symmetry. The basis can be a single atom or a group of atoms and must
at least express the full chemistry of the material. The lower diagram
shows the unit cell of an fcc material such as copper that has a basis
of a single copper atom. For the fcc lattice:
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| From:
Callister,
"Materials Science and Engineering," Wiley (1994) |
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