:term:`AO_BASIS <AO_BASIS (CCENERGY)>`
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      The algorithm to use for the :math:`\left<VV||VV\right>` terms If AO_BASIS is ``NONE``, the MO-basis integrals will be used; if AO_BASIS is ``DISK``, the AO-basis integrals stored on disk will be used; if AO_BASIS is ``DIRECT``, the AO-basis integrals will be computed on the fly as necessary. NB: The ``DIRECT`` option is not fully implemented and should only be used by experts. Default is NONE. Note: The developers recommend use of this keyword only as a last resort because it significantly slows the calculation. The current algorithms for handling the MO-basis four-virtual-index integrals have been significantly improved and are preferable to the AO-based approach. 

      * **Type**: string
      * **Possible Values**: NONE, DISK, DIRECT
      * **Default**: NONE