When the symmetry of a molecule is being worked out, the molecule is orientated by default. If NOREOR is specified, the molecule will not be reorientated. The main reason to not reorientate the molecule is to allow a lower point-group to be used, and to allow the x and y axes in Abelian groups to be defined by the user.

When GEO_REF is used, the default is that the reference geometry is rotated and translated to give the maximum overlap with the data-set geometry. This operation will be suppressed when NOREOR is present.

In a FORCE calculation, NOREOR will prevent the molecules being reoriented to line up the moment of inertia axes with the Cartesian axes.