The activation energy, E a , is calculated from the slope of the 2D fits of Equation 1 to the rate versus inverse temperature data shown in the ESI (Figure ). For TCP decomposition between the α-Fe(110) surfaces, E a increases with pressure from 20.6 ± 5.5 kJ mol 1 at 1 GPa to 24.0 ± 6.5 kJ mol -1 at 5 GPa. For the surfaces, E a again increases from 10.2 ± 7.2 kJ mol -1 at 1 GPa to 19.5 ± 3.63 kJ mol -1 at 5 GPa. A previous experimental study suggested that the thermal activation energy for TCP decomposition on stainless steel is approximately 60 kJ mol -1. Thus, the activation energy values are considerably underpredicted in our simulations compared to experiments, which is probably due to the chromium-rich oxide layer formed on the surface of stainless steel in experiments, which is known to be much less reactive towards TCP than iron oxides as used in our NEMD simulations. Thus, the chromium oxide surface formed on stainless steel is expected to reduce the activation energy by a smaller amount than the iron oxides formed on conventional bearing steel.