The trained ReaxFF force field describes the kink processes well (Figure and S4f), both when the atom leaves the site towards the terrace (0.72 eV vs. 0.91 eV/ 0.92 eV) and along the step-edge (0.44 eV/ 0.47 eV vs. 0.45 eV/ 0.46 eV). Analogous to the dimer systems, the force field underestimates the barriers for bond breaking (0.43 eV/ 0.46 eV vs. 0.63 eV/ 0.62 eV) for inner-corner processes (Figure and S4h) but overestimates bond formation barriers (0.21 eV/ 0.25 eV vs. 0.10 eV/ 0.08 eV). Precisely as in DFT, the exchange process at a 240°outer-corner (Figure ) exhibits a higher barrier than diffusion around the corner with the trained force field. However, unlike in the DFT reference data set, the OC 1 site is thermodynamically more stable than the OC 0 site. Furthermore, with the force field, the exchange processes are much better reproduced at the 300°outer-corners (Figure and S4j) than at the terrace, even though the barriers are still slightly overestimated. Finally, DFT predicts an almost barrier-free descent via the exchange process on [1120]-and [1120]steps (0.01 eV/ 0.02 eV; Figure and). Because the force field overestimates the exchange processes in general, the barriers to descent are generally higher (0.27 eV/ 0.13 eV).