| Abstract
| - The single-crystal structures of two incommensurate compounds, Ba1+x[(CuxRh1-x)O3] with x =0.1605 and x = 0.1695, were solved by a general method using the superspace group approach. A saw-toothfunction was used to model both the occupational and displacive modulations. This approach requires veryfew refineable parameters and leads to low residuals, R = 0.0370 and R = 0.0330 for x = 0.1605 and x =0.1695, respectively. The idealized structures of these two compounds consist of [(CuxRh1-x)O3]∞ chainscontaining groups of five face-shared (RhO6) octahedra separated by (CuO6) trigonal prisms. These chains inturn are separated from each other by [Ba]∞ chains. The idealized composition of both phases is Ba7CuRh5O18.Their modulated structures, described in the text, deviate from the ideal composition and structure. The approachused for the structure determinations of these compounds is completely general and can be applied to othermodulated composite structures of this series.
|
