Baudilio Tejerina @ on
Suppose you have an object (a molecule, for instance) and you need to know the point group it belongs to. The use of symmetry in QM speeds up the calculation an substantially reduces the computational resources needed to tackle these problems (memory, disk, CPU and wall times). The majority of the programs determinate the molecular symmetry by systematic trial-and-error of ("all") symmetry operator. A more elegant and even fastidious way to solve this important problem is by univocally determination of the symmetries of the molecule and from them the point group and the unique atomic set.