Crystal Lab › The 17 plane groups › Square
No. 11 p4mm
Square plane group · 8 symmetry operations per cell · 7 Wyckoff positions
Symmetry elements and Wyckoff positions (interactive)
No. 11 p4mm
SettingLoading the group…
x = 0.10, y = 0.17, z = 0.08
- Number
- 11
- Hermann–Mauguin symbol
- p4mm
- Lattice
- Square
- Operations per cell
- 8
- General position
- 8g (site symmetry 1)
Wyckoff positions (standard setting)
| Multiplicity | Letter | Site symmetry |
|---|---|---|
| 8 | g | 1 |
| 4 | f | ..m |
| 4 | e | .m. |
| 4 | d | .m. |
| 2 | c | 2mm. |
| 1 | b | 4mm |
| 1 | a | 4mm |
How to read it
- Each symmetry element drawn in the cell is worked out from the group’s operations. This is a two-dimensional group, so there are only rotation points and mirror or glide lines: rotation points are small filled shapes marked with their order (2, 3, 4 or 6), and mirror and glide lines run across the cell (dashed outline = glide). Colours: 2-fold red, 3-fold green, 4-fold blue, 6-fold purple.
- The multiplicity is how many equivalent points an atom on that site generates in the conventional cell; the general position has the highest multiplicity, equal to the number of operations.
- Site symmetry is the point group that leaves that position fixed; a special position (lower multiplicity) sits on a symmetry element — press + on a row to see its atoms land on the drawn elements.