In the next step, we investigated how increasing the number of vacancies affects Na + mobility based on structure C (Figure ) with composition Na1.625Zn0.625Al0.375Cl4. Similar to structure B, a significant Na + ion mobility was observed in the Na1(Zn/Al) layer according to MD simulations at 650 K. For structure C, the Na + density plot in Figure and 9e shows similar patterns as the plot for structure B in Figure and 9b, featuring a channel along the b axis and a zig-zag path along the c axis. And most importantly, the channel along the b direction is located exclusively in the Na1(Zn/Al) layer, yielding an activation barrier of 0.36 ± 0.05 eV from the Arrhenius plot (Figure ). The activation energy and diffusion rates were found to be comparable to the ones calculated for structure B but lower than experimental findings of EA ~0.450 eV for x = 0.625. The ionic conductivity calculated via equation 3 and under the same assumptions for Ni as for structure B is 0.21 mS/cm at a charge carrier concentration of 2.5 mol/l. This is only one order of magnitude above the experimental findings, indicating that structure C is a more realistic model to describe the mixture at x = 0.625 than structure B for x = 0.75.