:term:`CFOUR_SUBGROUP <CFOUR_SUBGROUP (CFOUR)>`
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      Specifies an Abelian subgroup to be used in a calculation. Acceptable arguments are DEFAULT (=0); C1 (= 1); C2 (= 2); CS (= 3); CI (= 4); C2V (= 5); C2H (= 6); D2 (= 7) and D2H (= 8). Use of C1 is of course equivalent to setting :term:`CFOUR_SYMMETRY <CFOUR_SYMMETRY (CFOUR)>` =OFF in the input. The DEFAULT option (which is the default) uses the highest order Abelian subgroup.

      * **Type**: string
      * **Possible Values**: DEFAULT, C1, C2, CS, CI, C2V, C2H, D2, D2H, OFF
      * **Default**: DEFAULT