We used ORCA v5.0.1 94 to calculate the transition states (TSes) and barrier heights of our best-performing codoped SACs because TeraChem does not support analytical Hessians. The TSes and barrier heights for the oxo formation and HAT step were modeled with the climbing image nudged elastic band (CI-NEB) method and bond length scan, respectively, followed by partitioned rational-function optimization (P-RFO) to locate transition state structures starting from a computed Hessian. For the bond length scan of the HAT step, the distance between the hydroxyl hydrogen and the methyl radical carbon was scanned from 2.0 to 1.0 Å in 0.1 Å decrements while fixing the distance between the metal-oxo oxygen and the methyl radical carbon atom and letting all other atoms relax. Then, the maxima obtained from NEB calculations and the bond length scan served as initial guesses for P-RFO calculations to locate the TS structures. TS identities were confirmed through frequency calculations (i.e., by the presence of a single imaginary frequency).