Rotation Matrices and Translation Vectors in 1. Every space group has a number of equivalent positions. Fd 3 m and Fd 3 c . The equivalent positions are listed for all space groups in International Tables for X-ray Crystallography . The equivalent positions are related to each other through symmetry operations .
Every symmetry operation is a pair of R and t .
One equivalent position is derived from another through a rotation and a translation applied in that order. The translations are along axes or diagonals of the unit cell.