Structural And Vibrational Study Of Cssbge3o9, A New Germanate In The Asbge(3)O(9) Family (A = Alkali Metal)

The germanate CsSbGe3O9, grown spontaneously via the high-temperature solution method from Cs2Mo4O13 used as a flux, crystallizes in the orthorhombic system with a = 12.3636(2), b = 13.8521(2), c = 31.4824(5) angstrom, and V = 5391.73(2) angstrom(3). Its structure, determined from single-crystal X-ray diffraction data, is most probably noncentrosymmetric despite our choice to report it in the centrosymmetric maximal supergroup Pnma D-2h(16) (no. 62) in which agreement factors R1 = 0.0371 and wR2 = 0.0706 (all data) were obtained. The unit cell contains 24 formulas CsSbGe3O9. The three-dimensional network is built up with regular germanate tetrahedra at nine crystallographically independent Ge sites. The Sb atoms (four independent positions) adopt octahedral coordination with O atoms, and the Cs+ cations are located in the channels of the 3-D network. A more in-depth analysis of the structure of CsSbGe3O9 is carried out in the light of the structures previously determined for the compounds ASbGe(3)O(9) (A = K, Rb) having the same chemical formula but significantly different atomic arrangements. The structural characteristics are discussed related to literature and the nature of the monovalent cation A(+).