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 = 860 K _database_code_amcsd 0007747 5.5659 5.6420 7.9322 90 89.989 90 P2_1/n 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 .02525 .02643 .02471 .00104 -.00011 .00038 Na1 0 0 .5 .04714 .04335 .04392 -.00400 -.00164 .00102 Na2 -.0065 .4694 .2520 .06677 .07038 .07084 -.00877 -.00089 .00240 F1 .0838 .0313 .2170 .07780 .09965 .03284 .00312 -.01190 -.00855 F2 .2356 .3231 .5387 .05290 .05871 .07926 -.02581 .01333 -.00187 F3 .1687 .2638 .9507 .06351 .04812 .09296 -.02010 .00034 .01992