The peak of the average temperature is reached at about 0.4 ns. From this point on, the thermostat extracts kinetic energy at a higher rate than the rate at which MgO formation releases energy. Nevertheless, the temperature at the surface of T surf,max = 985 K remains significantly higher than in the bulk phase of the cell (Figure ). At about 0.75 ns, equilibrium is reached, and MgO formation at the interface is complete, as underlined by molecular composition analysis (Figure ). The number of intact O 2 molecules in the atmosphere or adsorbed on the surface remains constant, which is also true for O-atoms bound in the MgO boundary phase. Similar trends as for Mg(0001) are also observed in simulations with Mg(1010)A and Mg(1011) surfaces in contact with oxygen; in fact, we found these surfaces to be even more reactive. The relative energy decreases the most for Mg(1010)A surface model and the oxidation penetrates the deepest, likely due to the more open surface structure. Over the course of oxidation, the average temperature reaches the highest values for Mg(1010)A and remains on a plateau for the longest time before decreasing again (Figure ). Similarly, molecular composition analysis in Figure shows that on Mg(1010)A, most O 2 molecules were decomposed and bound in the MgO phase, followed by Mg(1011) and finally Mg(0001) (Figure ). This trend aligns with the relative surface energy values, where Mg(1010)A and Mg(1011) surfaces are less stable than Mg(0001) (see Table ). could likely be observed by using significantly more surface layers, and by turning off the thermostat which dampens oxygen mobility increasingly the deeper that oxygen atoms penetrate into the slab. Fournier et al. also suggested that the surface oxide growth at 300 K follows an inverse logarithmic law. This is consistent with our observations that after initial contact, the surface is heated to such an extent that oxidation to deeper layers is facilitated.