Neumann's Principle
Neumann's principle
[′nȯi‚mänz ‚prin·sə·pəl]Neumann’s Principle
a postulate establishing the relation between the symmetry of the physical properties of a crystal and the symmetry of the crystal’s external form. According to the principle, the symmetry group of any physical property of crystals will include the symmetry elements of the point group of the crystal. The principle was established by F. E. Neumann.