Practical Electron Microscopy and Database

There are totally three lattice types which are:
         i) Primitive (P) lattices. In this case, there is only one lattice point per unit cell.
         ii) Body-centered (I) lattices. In this case, there is a lattice point at the corners and one in the center of the cell.
         iii) A-, B-, C- or F-centered lattices. In this case, there is a lattice point at the corners and others at one (A, B, C) or all three (F) of the faces.

For the enlarged tetragonal unit cells, i.e. C or F centred unit cells, the symbols selected to describe the symmetry with respect to the x and y axes, and with respect to the face-diagonal directions is simply the same as that selected for the equivalent P and I centred cells, but with the order of the symbols reversed e.g. the name C4/mmb is used for the enlarged unit cell of space group P4/mbm.