Although not explicitly included in the Arrhenius form, we hypothesize that these trends can be rationalized based on the higher attempt to diffuse frequency of CH 3 as shown in equation 5. Specifically, equations 4 and 5, show that the rate of surface diffusion is correlated with the diffusion jump length and attempt frequency. It is also interesting to note that C shows low diffusivity despite a small diffusion barrier. We expect that this behaviour is likely due to the jump frequency being quite low for carbon as observed by the low intercept, implying carbon rarely jumps between sites leading to a lower average E app d . Since this E app d intrinsically includes a measure of the diffusion attempt frequency and is not restricted to a particular pathway as would be the case with an NEB, these values are likely the "true" diffusion barriers for an adsorbate over the Ag (111) surface. Similar arguments could explain the higher apparent E app d for CH than C. The apparent diffusion energy barrier for CH is higher than that of C. We hypothesize that this is likely because not all valence electrons are engaged in binding to Ag and this was previously observed by Mavrikakis et al. Taken together, the above discussion further highlights the advantages of using MD simulations (rather than a hTST framework) for investigating surface diffusion.