Explanation

Symmetry operation according to the symmetry elements of crystal (including macro symmetry elements and micro symmetry elements) can make the equivalent parts of the crystal coincide regularly. There are four types of macroscopic symmetry elements: center of symmetry, axis of symmetry, plane of symmetry, and opposite axis. By symmetry operation of macro symmetry elements, 32 point group can be combined, which determines the geometric polyhedron shape of an ideal crystal; There are three kinds of micro symmetry elements: lattice, spiral axis and slip plane. 230 kinds of space group can be combined by symmetry operation of microscopic symmetry elements, which determines the internal structure of all ideal crystal.

Classification