The mobility of the Na + in mixtures Na1.75Zn0.75Al0.25Cl4 and Na1.625Zn0.625Al0.375Cl4 based on its NZC-type structure was first evaluated with MD simulations. Two distinct model configurations of Na1.75Zn0.75Al0.25Cl4, either containing only Na1(Al) vacancies (Figure , denoted as structure A) or only Na2(Al) vacancies (Figure , denoted as structure B) were chosen as representatives for the layer-like structure type that was calculated previously to be most stable. The model shown in Figure was taken as a base for the model of structure C with composition Na1.625Zn0.625Al0.375Cl4 (Figure ), whose Na site occupations are close to the ones obtained from X-ray diffraction results (Na1 Occ. = 0.71(4), Na2 Occ. = 0.95(4), Figure ). Here, structure C is composed of half-filled Na2(Zn/Al) adjacent to the entirely vacant Na1(Al) layer. It is worth emphasizing that all the model structures have somewhat idealized site occupancies, close but not identical to the experimentally observed ones, which are applied for the sake of simulation simplicity. For the most stable Na1.75Zn0.75Al0.25Cl4 structure with solely Na1 vacancies (Figure ), limited ion movement between sites was observed by MD simulations. The distribution of sodium in structure A at 700 K is visualized in Figure . The only movement that was found takes place along the a-axis locally restricted between vacant Na1 positions in the Na1(Al) layer and the adjacent Na2 positions.