Normally, anion-anion peaks are not coincident with anion-cation peaks because of Coulomb interactions, sometimes referred to as charge alternations. It is also noted that the partial S(Q) of Cs shows a peak just below 2 Å 1 . We attribute this peak to the peak at 2 Å 1 in the experimental S(Q) shown in Fig. . As mentioned above, AIMD simulations are not well suited for the low-Q region due to the small size of the simulation box.