CRYSTAL-STRUCTURE OF TE3NB2O11

Te3Nb2O11 crystallizes in space group P21212 with a = 7.700(2), b = 15.700(3), c = 3.980(1) Å, and Z = 2. Full matrix least squares refinement gave an R value of 0.033 using 521 independent reflections. Infinite double NbO octahedra, sharing corners, are connected via finite. {A figure is presented}. strings, to form a three-dimensional net. The threefold coordinated Te(IV) atom has the normal pyramidal configuration (TeO = 1.84, 1.86 and 1.86 Å), while the fourfold coordinated Te(IV) atom has an unusual configuration in which the centre of the Te(IV) atom is placed within a tetrahedron of oxygen atoms. The average NbO bond distance of 2.00 Å is normal. However, the Nb atom is displaced from the centre of the oxygen octahedron along the polar axis (chain direction), to give alternating short and long NbO distances of 1.80 Å and 2.19 Å, respectively. © 1979.