This keyword controls the symmetry analysis of the molecular structure.
NONE No symmetry transformations are performed.
OFF The symmetry analysis is switched off.
ON A symmetry analysis is performed.
With the option ON of the SYMMETRY keyword a symmetry analysis is performed. In this case the point group of the molecule is detected automatically and the molecular INPUT ORIENTATION is transformed into the STANDARD ORIENTATION defined by the center of mass and the principal axes of the inertia tensor. All further calculations are done in this orientation. This is the only way to obtain symmetry adapted tensor components e.g. for electrostatic moments (see 4.8.3) and polarizabilities (see 4.8.4). For atomic calculations, the ON option of the SYMMETRY keyword enforces the zeroing of those off-diagonal Kohn-Sham elements which connect (atomic) orbitals of different spherical symmetry.

With the default option NONE of the SYMMETRY keyword no symmetry transformation is performed but the point group of the molecule is detected. The INPUT ORIENTATION is used for the SCF calculation. However, if a frequency analysis is requested (see 4.8.1), the normal modes are always printed in STANDARD ORIENTATION. Also a Bader population analysis (see 4.9.1) is always performed in STANDARD ORIENTATION. The option OFF of the SYMMETRY keyword skips the symmetry analysis module and assigns a C$_{\rm 1}$ point group for the input structure. This setting is advisable for systems with more than 1,000 atoms.