:term:`CFOUR_CONTRACTION <CFOUR_CONTRACTION (CFOUR)>`
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      Specifies the contraction scheme used by the integral and integral derivative program. SEGMENTED (=0) uses a segmented contraction scheme; GENERAL (=1) uses a general contraction scheme, and UNCONTRACTED (=2) uses the corresponding uncontracted sets. Note that even for truly segmented basis sets, the integral programs run significantly faster in the GENERAL mode.

      * **Type**: string
      * **Possible Values**: SEGMENTED, GENERAL, UNCONTRACTED
      * **Default**: GENERAL