Cryolite Yang H, Ghose S, Hatch D M Physics and Chemistry of Minerals 19 (1993) 528-544 Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Sample: T = 890 K _database_code_amcsd 0007749 5.6323 5.6270 7.9580 90 90 90 Immm atom x y z B(1,1) B(2,2) B(3,3) B(1,2) B(1,3) B(2,3) Al 0 0 0 .02372 .02176 .02917 0 0 0 Na1 0 0 .5 .10646 .04986 .04427 0 0 0 Na2 0 .5 .2515 .10782 .07195 .08872 0 0 0 F1 0 0 .2192 .26249 .19499 .02296 0 0 0 F2 .2335 .2166 0 .15988 .11268 .21482 -.07917 0 0