Here, we have investigated the structure and fluorideion dynamics of the cation-disordered fluorite cubic (c-)BaSnF 4 . Rietveld refinement of XRD data confirms an average fluorite structure with {Ba,Sn} disorder (Fig. ). 119 Sn Mössbauer spectroscopy demonstrates the presence of stereoactive Sn(II) lone pairs, and totalscattering PDF data show clear deviations from the average fluorite structure at short range (Fig. ).