CRYSTAL-STRUCTURE OF LEAD GERMANATE PB11G E3O17

The crystal structure of the synthetic compound Pb11Ge3O17, M(r) = 276 9.0, has been determined based on 16134 intensity data; R = 0.065, R(w ) = 0.072. Monochromatized synchrotron radiation of wavelength 1.198 A ngstrom was used for data collection. The compound crystallizes tricli nic in the space group <P(1)over bar> with lattice parameters a = 22.2 59(4) Angstrom, b = 19.910(4) Angstrom, c = 7.361(1) Angstrom, alpha = 97.59(1)degrees, beta = 95.15(1)degrees, gamma = 92.35(2)degrees; V = 3215.8 Angstrom(3), Z = 6, D-x = 8.579 Mg m(-3). As in PbO and other examples of lead germanate oxides with nongermanate O atoms, the Pb an d Ge atoms are arranged like a cubic close packing of spheres. The fcc -like sequence of layers parallel to (100) is, however, interrupted af ter every fifth layer by two layers of hcp-like sequence: ccccchhccccc hh ... Taking the crystal structure into account, the chemical formula should be written as Pb-11[GeO4][Ge2O7]O-6.