Fig. shows X-ray di↵raction patterns for molten FLiNaK and FLiNaK-CsF (5mol%). The results are compared with molecular dynamics simulations. The simulation results follow the measurements closely, including the main peak at ⇠2.5 Å 1 and the peak at ⇠2 Å 1 . The latter is significantly enhanced in the presence of Cs, as expected due to the large relative size of the Cs ion and it's higher X-ray scattering cross-section.