:term:`CFOUR_FROZEN_VIRT <CFOUR_FROZEN_VIRT (CFOUR)>`
"""""""""""""""""""""""""""""""""""""""""""""""""""""

      Specifies whether in the correlation treatment all virtual orbitals (OFF =0) or only a subset of virtual orbitals (ON =1) are used. In the latter case, the threshold for deleting virtual orbitals based on the orbital energy needs to be specified in a ``%frozen_virt`` section.

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

