:term:`NAT_ORBS_T2 <NAT_ORBS_T2 (SAPT)>`
""""""""""""""""""""""""""""""""""""""""

      Do use MP2 natural orbital approximations for the :math:`v^4` block of two-electron integrals in the evaluation of second-order T2 amplitudes? This approximation is promising for accuracy and computational savings, but it has not been rigorously tested.

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