Select here the parameters to measure the point symmetry.
### Periodicity

When the **No** option is chosen (the default), all elements
of symmetry are taken into account, and the chemical
point group is determined. When the **Yes** option
is chosen, all elements of symmetry related with rotations
of order different from 6, 4, 3, 2 are ignored. The reported
crystallographic point group is thus the maximum point symmetry
that could be achieved in the center of this aggregate, if it
was in a periodic crystal.
### Tolerance

The elements of symmetry of a group depend entirely of the
tolerance applied to the operations of symmetry. GAMGI uses
the same tolerance for all operations: the maximum distance
that is tolerated between initial and transformed coordinates.

For example, a C5v chemical group becomes a Cs crystallographic point group because after discarding the C5 axis, only one of the five mirror planes can be considered as a true element of symmetry in a periodic system. A chemical Ih becomes a Th crystallographic group, because after discarding the C5 axes, the remaining planes and axes form five different sets of cubic Th symmetry, although only one can be considered at a time.

Everytime the chemical group is found, the crystallographic group can also be determined. Usually this crystallographic group is not unique. For example, a D12h chemical group can be either a D4h or a D6h crystallographic group. GAMGI shows the various crystallographic groups that cover all the possible operations of symmetry, in sequence, with their symmetry operations and symmetry elements. In particular, chemical C0v becomes C4v or C6v, chemical D0h becomes D4h or D6h and chemical Kh becomes D4h or D6h or Oh crystallographic groups respectively.

GAMGI tries to find all the symmetry elements independently,
and in general each of these elements requires a different
tolerance. Thus, for a given tolerance, some elements
may be recognized and others may go missing, resulting in
an inconsistent set of symmetry elements. When this happens,
the group is reported **Undefined**. The solution is to
increase the tolerance (so valid elements might be found)
or to decrease it (so fake elements might be discarded).

When the transformed coordinates for a given symmetry element
are closer than the **Initial** tolerance, GAMGI attempts
to optimize the symmetry element, to get transformed coordinates
closer than the **Final** tolerance. When the transformed
coordinates do not pass the **Initial** tolerance or when
the optimization fails, the attempted element is discarded.
When the transformed coordinates pass the **Final** tolerance,
the element is accepted.

During optimization, GAMGI will never attempt to change the atoms,
only the symmetry elements. To disable optimization, just set
**Initial** equal to **Final** tolerance.