A preliminary molecular dynamics (MD) simulation was performed on the LaSrMnO4F0.9 composition. This composition, according to the experimental and computational data presented in this work, lies within a single-phase region and thus the model was constructed by adding randomly distributed vacancies of fluoride ions in the system, as described in section 2. Visual analysis of the fluoride ions trajectory derived from the MD simulation revealed that, at the explored temperature, the fluoride diffusion mechanism operates through vacancies hopping (Figure ). Notably, this diffusion process is predicted to be anisotropic, since it is confined to the fluoride layers within the ab plane, with no interlayer diffusion observed.