The TCP decomposition rates vary significantly depending on the surface chemistry, with the fastest dissociation being observed for the α-Fe(110) systems, followed by Fe 3 C(010), and finally Fe 3 O 4 (100). This may be due to the differences in surface energies of the three ferrous surfaces. Higher surface energies promote stronger molecular adsorption and thus faster TCP decomposition. DFT calculations have shown that adsorption is a crucial step the decomposition of TCP on iron surfaces. Disso- ciative chemisorption is the rate-determining step for many heterogeneously catalysed processes. Previous experimental thermal decomposition studies showed that TCP preferentially reacted with iron oxides that were in a higher oxidation state, i.e. Fe < FeO < Fe 3 O 4 < Fe 2 O 3 . This contrasts with first principles NEMD simulations of other lubricant additives, such as molybdenum dithiocarbamates, where native iron surfaces were found to be much more reactive than oxidised surfaces. In agreement with the simulations by Peeters et al. , we observe much higher mechanochemical reactivity on the iron surface compared to the iron oxide surface.