All kinetic Monte Carlo (kMC) simulations were performed within the ReaxFF implementation of the Amsterdam Modeling Suite 2021.1 . A 100x100 Li(100) and Na(100) slab was utilised to simulate the initial growth processes applying periodic boundary conditions in x-and y-directions. In all simulations, the maximum number of iterations was set to 1 × 10 9 . The diffusion constants were determined from an ensemble of 20 kMC calculations to increase the statistical significance of the results.