Evaluate the error function: In this part, the developed KVIK approach will be utilised to optimise a reactive force field potential for metallic sodium and lithium and their interaction. For this purpose, the proposed training set will be generated with the data from our previous work . Subsequently, a multi-scale model will be applied to investigate the initial growth processes on the stable surfaces of both metals using kMC simulations. The required activation energies and pre-exponential factors of the respective processes will be calculated utilising the developed reactive force field potential. For these systems, the major challenge in optimising the force field parameters is the subtle energetic differences between the various diffusion processes.