Crystal symmetry (Crystal Pattern): I

Abstract

We have already introduced the space lattice and the symmetry elements that are possible in the space lattices. It has also been mentioned that when a pattern is constituted by placing the motifs in the lattice sites, these symmetry elements originally present in the space lattice of the pattern may be reduced due to the shape of the motifs; however, this is not true only when the motifs are isotropic in their shape. If the motifs are atoms or molecules then the pattern itself is a crystal. Therefore, the crystals can be regarded as three-dimensional patterns. When some of the symmetry elements present in the corresponding space lattices are also present in the crystal, they are named as macroscopic symmetry elements as they are manifested by the regular external faces of the crystals and as most of them can be studied by unaided eye by observing the single crystal faces. These macroscopic symmetry elements present in a crystal can be once again recalled as in Table 4.1.