THALLIUM TUNGSTATE TL2W4O13 - TUNNEL STRUCTURE RELATED TO THE HEXAGONAL TUNGSTEN BRONZE

The crystal structure of thallium tungstate Tl2W4O13 (a = 7.327Å; b = 37.864 Å; c = 3.840 Å; space group Pmab) has been resolved by three-dimensional single-crystal X-ray analysis. The average structure was resolved by standard Patterson and Fourier techniques and refined by full-matrix least squares to final agreement indices R = 0.087 and Rw = 0.100. Superstructure reflections referred to a supercell (a, b, 2c; space group Pcab) led to a framework model which is described. The structure consists of corner-sharing chains of WO6 octahedra parallel to a and c axes. Hexagonal and pentagonal tunnels, bound by these chains, are filled by thallium atoms. The atomic arrangement is closely related to the hexagonal bronze structure. The tungstate Tl2W4O13 can thus be considered as a member of a series of phases (TlB3X9)n · Tl6B10X34 (X = O, F) involving hexagonal tungsten bronze ribbons. © 1979.