Question

I was wondering what the significance of space groups in X ray cyrstallography. How does it contribute to determining the structure? please keep it brief Like if it said Space group: P 32 2 1, what would that represent

Answer 1

International Union of Crystallography introduce tables of all space group types, and assigns each a unique number from 1 to 230,these groups each having a point groups of unit cell

The Hermann–Mauguin (or international) notation describes the lattice and some generators for the group. It has a shortened form called the international short symbol, which is the one most commonly used in crystallography, and usually consists of a set of four symbols. The first describes the centering of the Bravais lattice (P, A, B, C, I, R or F). The next three describe the most prominent symmetry operation visible when projected along one of the high symmetry directions of the crystal. These symbols are the same as used in point groups, with the addition of glide planes , screw axis, . By way of example, the space group of quartz is P3₂ 21, showing that it exhibits primitive centering of the motif (i.e., twice per unit cell), with a threefold screw axis and a twofold rotation axis & P3₂ 21, it is trigonal.Therefore we are able to represent the structure of a a crystal with the help of point groups