Crystal Symmetry

Abstract

It is important from many points of view to understand and to be able to describe clearly the symmetry of a crystal. For example, the knowledge that there is a mirror plane in the unit cell of a structure implies that the positions of only half the atoms need be determined in order to fully describe the structure. Knowledge that there is an inversion center in the diffraction pattern makes it necessary to measure only half of the available reflections. The symmetry of a crystal has many effects on its physical characteristics, such as its optical and electrical properties. Finally, errors in determining the symmetry of a crystal can lead to its structure being impossible or difficult to solve. From almost any point of view, it is crucial to determine the symmetry of a crystal and to describe it correctly.