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 = 673 K _database_code_amcsd 0007743 5.5022 5.6284 7.8725 90 90.055 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 .01945 .01900 .01648 -.00025 .00024 -.00100 Na1 0 0 .5 .03430 .03111 .02897 -.00549 -.00115 .00182 Na2 -.0093 .4576 .2517 .04924 .04434 .04934 -.00780 .00013 .00104 F1 .0944 .0398 .2180 .05013 .05849 .02056 .00215 -.00719 -.00530 F2 .2310 .3262 .5423 .03498 .03957 .04757 -.01588 .00704 -.00164 F3 .1651 .2668 .9430 .04057 .03349 .05550 -.01306 .00131 .00830