We now compare the charge transfer coefficient for our force-based method with the cell extrapolated value for a few prototype electrochemical reactions. To do so, we perform electrochemical barrier calculations for three reactions, C * + H + + e -→ CH * (this work), OH * + H + + e -→ H 2 O and H * + H + + e -→ H 2 (from Ref 14, 16). Figure shows a parity plot between the q obtained from Equation and Figure : Parity plot for q from fitting through Equation 4 for a series of increasingly larger unit cells and through the force-based method as in Equation ; dashed line indicates exact fit and green band indicates ± 0.1 error with either methodology. Alternative ω denotes an idealised reaction path where the proton descends directly to the surface along the direction of the surface normal.