Mosers C-Line, the Apparent Multiplicity m and Modules in Descriptions of Ta2O5 and Related Structures

The complex oxide Sr7Re4O19 has been synthesized and its crystal structure was determined by X-ray diffraction powder data analysis (space group C2/m; a=13.6379(3) ?, b=5.6035 (2) ?, c=10.3700(3) ?; beta=98.348(2)°, Z=2, RI=0.018, RP=0.050). The compound crystallizes in a new structure type, which can be derived from the Ba7Ir6O19 structure by removing the Ir atoms from the middle octahedron of three face-sharing IrO6 octahedra units. This change results in the infinite cis-bridged chains of the ReO6 octahedra linked together by common corners. Each chain is connected with another one by the corner-sharing of each second ReO6 octahedron. The 10- and 12-coordinated Sr atoms are situated between these infinite structure fragments. Magnetic properties of the Sr7Re4O19 compound were studied by SQUID measurements