plassgruppe
Plassgruppe, in crystallography, refers to the symmetry group that describes all symmetry operations leaving a crystal lattice invariant in three-dimensional space. In English, the term is space group. A plassgruppe combines the translational symmetry of the crystal lattice with point-group operations such as rotations, reflections, inversion, as well as glide reflections and screw axes that couple translation to rotation or reflection. The space-group symmetry constrains the arrangement of atoms in the crystal and determines many physical properties as well as the patterns seen in X-ray, neutron, or electron diffraction.
There are 230 distinct plassgrupper in three dimensions. They are categorized according to the seven crystal
In practice, knowing the plassgruppe of a crystal helps in solving and refining crystal structures, interpreting