In recent years, the fluorite-structured solid solutions with the general formula, (MF₂)_1–𝑥(RF₃)_𝑥 (M = Ca, Sr, Ba, Pb and R is a rare-earth element or Y), have been the subject of numerous experimental studies focussed on their superionic properties. The overall cubic crystal symmetry (space group 𝐹𝑚3𝑚) is conserved up to 𝑥 ≤ 𝑥_max, where 𝑥_max 0.4–0.5 depending on M and R. The zone centre phonons and phonon dispersion along three symmetry directions of the mixed superionic compound (BaF₂)_1–𝑥(LaF₃)_𝑥 have been investigated by applying de Launey angular force model for 𝑥 ≤ 𝑥_max. The calculated results are compared and explained with available experimental results.