Mixed halide sodalites

Na 8 (AlSiO 4 ) 6 (Cl,Br) 2 , M r =969.0 to 1057.9, cubic, P43n, a 0 =8.8812(3) to 8.9304(3) A, V=700.5(1) to 712.2(1) A 3 , Z=1, D x =2.29 to 2.47 gcm −3 .Na 8 (AlSiO 4 ) 6 (Cl,I) 2 , Mr=969.0 to 1151.9, cubic, P43n, A 0 =8.8812(3) to 9.0138(4) A, V=700.5(1) to 737.1(1) A 3 , Z=1, D x =2.29 to 2.38 gcm −3 . The structures of the mixed anion sodalites Na 8 (AlSiO 4 ) 6 (Cl,Br) 2 and Na 8 AlSiO 4 ) 6 (Cl,I) 2 have been refined from powder neutron diffraction data