After the formation of initial polyatomic clusters, we would like to discuss further surface growth, especially island formation, by studying additional processes of the terrace-step-kink (TSK) model (step-edge, step-vacancy, kink, inner-corner, and outer-corner). The TSK model describes the diffusion processes taking place during surface growth and discusses several growth mechanisms. As described previously, islands on Mg(0001) are more stable on hcp sites starting from a heptamer. Thus, only processes at hcp steps, kinks, and corners were investigated, which consist of more than 7 atoms. A detailed overview of the processes studied may be found in Table , Figure , and Figure for Mg(0001) and Table XII, and Initially, we want to discuss the process of a free atom approaching the step-edge on Mg(0001). As we have already seen with similar dimer and trimer processes, the forward barrier is negligibly small, but the detachment barrier is many times higher On Mg(101 ! 1), it is noticeable that an approaching atom hast to overcome higher forward barriers of at least 0.14 up to 0.44 eV, depending on the direction of the step. However, this behavior is expected since the barriers for terrace self-diffusion on Mg(101 ! 1) are already at least 0.30 eV. The ratio between forward and reverse barriers is between 1-4 times, significantly lower than for Mg(0001) (25-40 times).