It was shown that the mobility of fluoride ions in nanocomposite depends on the shape of nanoclusters of dopants. Fluoride diffusion in Рb_1-xCd_xF₂–SiO₂ nanocomposites has been simulated by molecular dynamics. Nanoscale particles of the composite were constructed from spherical nanoparticles of the Pb_0.7Cd_0.3F₂ solid solution with a diameter of 4 nm and surrounded by Si₃O₆ clusters. The diffusion coefficient of fluoride ions has been calculated in the n(SiO₂)₃–Pb_0.7Cd_0.3F₂ heterosystem with linear and cyclic Si₃O₆ clusters. It has been shown that the interaction between nanoparticles of the fluoride solid solution and Si₃O₆ clusters leads to an increase in the mobility of fluoride ions in the nanocomposite material.