:term:`CFOUR_REFERENCE <CFOUR_REFERENCE (CFOUR)>`
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      Specifies the type of SCF calculation to be performed. RHF (= 0) requests a restricted Hartree-Fock reference; UHF (= 1) an unrestricted Hartree-Fock reference; ROHF (= 2) a restricted open-shell Hartree-Fock calculation; TCSCF (=3) a two-configurational SCF calculation, and CASSCF (=4) a complete-active space SCF calculations (currently not implemented). **Psi4 Interface:** Keyword subject to translation from value of :term:`REFERENCE <REFERENCE (SCF)>` unless set explicitly.

      * **Type**: string
      * **Possible Values**: RHF, UHF, ROHF, TCSCF, CASSCF
      * **Default**: RHF

