where E tot is the total energy of the interacting system, E slab is the total energy of the adsorbate-free surface slab, and E atom is the energy of the free-atom reference. Table summarises the calculated energy values of ReaxFF and DFT-PBE. Our parameterised potential function can reproduce the thermodynamic stability se-quence of the adsorption sites on the respective surfaces for both metal systems. We also found an excellent agreement between the absolute adsorption energies generated with the optimised reactive force field and the DFT-PBE target values. The deviations between the pairs of values are well within the range of the computed standard deviation from DFT. Note that the adsorption properties of the bridge and ontop positions on Na(111) and Li(111) were correctly determined by ReaxFF without being included explicitly in the training routine.