Perovskite-like modification of Cs3Sb2I9 as a member of the OD family A(3)B(2)X(9)

The structure of the trigonal modification of Cs3Sb2I9 was refined by XRD m ethods (Syntex P (1) over bar diffractometer, lambda MoKalpha) at T = 285 K . The structure is of perovskite type A(3)B(3-x)X(9) with ordered vacancies in the B-sublattice. The unit cell with pseudo-R-centering has the followi ng parameters: a = 8.435(7) c = 10.390(7) Angstrom, V = 151.8 Angstrom(3), Z = 1; d(x) = 4.67 g/cm(3). The centrosymmetric space group P (3) over bar m1 was chosen based on the laser radiation second harmonic generation rest. The parameters of the pseudo-rhombohedron corresponding to the perovskite cell are a' = 5.976 Angstrom, alpha = 89.78 degrees The R-lattice of a pero vskite structure is disturbed by ordered Sb vacancies in one of the three I -6 octahedra. The structural modifications of the compounds A(3)B(2)X(9) ar e analyzed in terns of Dornberger-Schiff's OD theory as the members of the family formed by the two-dimensional periodic fragments of perovskite type structures.