# CFOUR_METHOD

> 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 optking keywords instead, particularly OPT_TYPE and STEP_TYPE

> - Type: string
> - Possible Values: NR, RFA, TS, MANR, SINGLE_POINT
> - Default: SINGLE_POINT