Importance of true satellite reflections in the analysis of modulated, composite crystal structures .2. The structure of [M'2Cu2O3](7)[CuO2](10), M'=Bi0.04Sr0.96

The structure of the modulated, composite crystal bismuth strontium cuprate [M(2)'Cu2O3](7)[CuO2](10), with M' = Bi0.04Sr0.96, has been determined and refined using a model which allows modulation of the atomic positional parameters for all atoms, as well as modulation of thermal parameters for the M' site. The structure is orthorhombic, with c being the misfit direction and a = 11.4712 (6), b = 13.3765 (13) Angstrom. Sublattice 1, of composition (CuO2)(4), has c(1) = 2.7509 (10) Angstrom, while sublattice 2, of composition (M(2)'Cu2O3)(4), has c(2) = 3.9316 (3) Angstrom. Superspace group Amma(001 + gamma)ss(1) over bar; q = gamma c(1)* with gamma = 0.6997 (3); lambda = 0.6565 Angstrom, mu = 25.4 mm(-1). The final residual is R(all) = 0.0474 for all 1174 reflections, R(main) = 0.0451 for the 549 main reflections, R(1.sat) = 0.0562 for the 442 first-order satellite reflections and R(2.sat) = 0.1044 for the 183 second-order satellite reflections. The satellite reflections have been collected with X-ray synchrotron radiation. It is shown that these reflections help to unambiguously determine the superspace group. The orthorhombic compound has a layered structure, stacked along the b axis. The first sublattice consists of layers of CuO2 ribbons, with CuO4 squares sharing edges along the c axis. The second sublattice consists of CuO4 squares, which are sharing edges in a zigzag pattern. In-between these layers the disordered layers of Bi and Sr atoms are sandwiched. A comparison with structurally and chemically related compounds is made.