Figure 5b shows the BT partial structure factor S^{BT}_{NC}(k) from experiment at T = 1100 K and the PIM simulation at T = 1100 K.  Also shown is the breakdown of the simulated function into its contributions from the weighted Faber-Ziman partial structure factors S^{FZ}_{ClCl}(k), S^{FZ}_{NaCl}(k) and S^{FZ}_{NaNa}(k). The inset highlights the measured and simulated BT functions at low-k, plotted as a function of k^2 in order to extract the low-order moments by fitting a straight line.