CUYB2GE4O12, A NEW BIDIMENSIONALLY TUNNELED STRUCTURE

Employing CuO as self flux crystals of CuYb2Ge4O12 have been grown for the first time, The crystal structure of CuYb2 Ge4O12 has been determ ined by single-crystal X-ray diffraction in the triclinic P (1) over b ar (No. 2) space group to an R value of 6.1%, with a = 7.156(2) Angstr om, b = 7.937(3) Angstrom, c = 4.905(3) Angstrom, alpha = 86.63(3)degr ees, beta = 102.41(4)degrees, gamma = 114.12(3)degrees, V = 248.2(2) A ngstrom(3), Z = 1, and D-c = 5.97 gcm(-3). The novel tridimensional Cu Yb2Ge4O12 structure type can be conceived as formed by layers of (GeO4 )(4) units of vertex-sharing GeO4 tetrahedra, chains of YbO7 polyhedra , and isolated CuO4 squares connecting (GeO4)(4) units, with channels or tunnels of size up to 4.08 Angstrom in the a and c directions. A co mparison is made between the structure types of the title germanate an d recently reported CuNd2Ge2O8. The temperature dependence from 350 to 1.8 K of the reciprocal de magnetic susceptibility for CuYb2Ge4O12 is shown and presents a deviation from linearity over the whole temperat ure range. The infrared spectrum between 1000 and 100 cm(-1) is given and related with those of comparable species. (C) 1996 academic Press, Inc.