# CFOUR_ANH_SYMMETRY

> Specifies whether nonabelian symmetry is to be exploited in determining displacements for CFOUR_ANHARMONIC =VIBROT or VPT2 calculations. If set to NONABELIAN (=0), maximum advantage will be taken of symmetry and the full set of cubic force constants will be generated from a skeleton set by application of the totally symmetric projection operator. If set to ABELIAN (=1), only the operations of the abelian subgroup will be exploited. Note: It is important to point out that the symmetrization currently works only for cubic constants. Therefore, if you require quartic force constants (for frequency calculations), you must use the ABELIAN option. Moreover, the latter work for only asymmetric tops and linear molecules.

> - Type: string
> - Possible Values: ABELIAN, NONABELIAN
> - Default: ABELIAN