2012 | OriginalPaper | Buchkapitel
4. Crystal Structure
Erschienen in:
Crystallography
Abstract
In order to progress from a lattice to a crystal, the points of the lattice must be occupied by atoms, ions or molecules. Because the points are all identical, the collections of objects occupying them must also be identical. In general, crystals are not built up so simply as the crystal of α -polonium in Fig. 3.1!
Let us consider the construction of a crystal by means of a hypothetical example. Figure 4.1a shows a lattice with a rectangular unit cell projected on the a, b-plane. We now place the molecule ABC in the unit cell of the lattice in such a way that A lies at the origin and B and C within the chosen cell (Fig. 4.1b).
The coordinates are yet another triple: x,y,z, where 0 ≤ x,y,z < 1 for all positions within the unit cell.