point group
Noun
Meaning
point group (plural point groups)
(mathematics) A group of isometries leaving a fixed point.
Examples
For example, halite (NaCl), galena (PbS), and periclase (MgO) all belong to the hexaoctahedral point group (isometric family), as they have a similar stoichiometry between their different constituent elements.
Point groups The crystallographic point group or crystal class is the mathematical group comprising the symmetry operations that leave at least one point unmoved and that leave the appearance of the crystal structure unchanged.
Kyanite is triclinic, while andalusite and sillimanite are both orthorhombic and belong to the dipyramidal point group.
Space groups In addition to the operations of the point group, the space group of the crystal structure contains translational symmetry operations.
In order to assign a point group for any given molecule, it is necessary to find the set of symmetry operations present on it.
The general procedure for constructing a molecular orbital diagram for a reasonably simple molecule can be summarized as follows: 1. Assign a point group to the molecule.