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

      Specifies the geometry optimization strategy. Four values are permitted: NR (=0) -- Straightforward Newton-Raphson search for minimum; RFA (=1) -- Rational Function Approximation search for minimum (this method can be used to find minima when the initial structure is in a region where the Hessian index is nonzero); TS (=2) Cerjan-Miller eigenvector following search for a transition state (can be started in a region where the Hessian index is not equal to unity); MANR (=3) -- Morse-adjusted Newton-Raphson search for minimum (very efficient minimization scheme, particularly if the Hessian is available); 4 is currently unavailable; SINGLE_POINT (=5) is a single point calculation. **PSI4 Interface:** Geometry optimizations run through PSI (except in sandwich mode) use PSI's optimizer and so this keyword has no effect. Use :ref:`optking <apdx:optking>` keywords instead, particularly :term:`OPT_TYPE <OPT_TYPE (OPTKING)>` and :term:`STEP_TYPE <STEP_TYPE (OPTKING)>` 

      * **Type**: string
      * **Possible Values**: NR, RFA, TS, MANR, SINGLE\_POINT
      * **Default**: SINGLE\_POINT

