Our parameterised potential function can correctly reproduce the stability sequence of the respective sodium and lithium bulk phases. Moreover, we found excellent agreement between the structural and energetic data from DFT-PBE and ReaxFF. For the respective bulk moduli, minor deviations of a few GPa could be observed; however, their fluctuations are within the error range of the DFT . Although the low-temperature phase hr9 was not included in the training set, the crystal structure is correctly reproduced by ReaxFF. This indicates a good transferability of the developed parameter set.