The black line drawn from *H to *OH indicates the path that the *H atom effectively followed in a Grotthus-like mechanism. Sampling of the region from the initial state (H2O) to the transition state and early final state was found to be sufficient to estimate the forward Volmer barrier. We calculate this value by first calculating the barrier energy for each timestep from the difference between the initial state basin minimum and the transition state region maximum. The maxima of this function correspond to the points just before the system crosses from the initial state to the final state, where the bias potential is sufficient for the system to overcome the barrier. Figure shows the evolution of the CVs during metadynamics sampling and Figure shows the corresponding barrier energy evolution. The black lines on the CV plot and the points on the energy plot correspond to these crossing points. Figure The barrier energies in Figure were measured to be 1.36 eV at 300K and 1.19 eV at 100K. The 0.17 eV difference here corresponds to an increase in entropic contributions with temperature. It appears that a consistent hydrogen bonding environment comparatively stabilizes the transition state. The system is in the initial state for a much longer period than the transition state, so such differences in stabilization are inherently broken, while the liquid-like interface will have some number of crossings without hydrogen bonding.