:term:`NAT_ORBS_V4 <NAT_ORBS_V4 (SAPT)>`
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      Do use MP2 natural orbital approximations for the :math:`v^4` block of two-electron integrals in the evaluation of CCD T2 amplitudes? Recommended true for all SAPT computations.

      * **Type**: :ref:`boolean <op_c_boolean>`
      * **Default**: false