CRYSTAL-STRUCTURE OF CS2V4O11 WITH UNUSUAL V-O COORDINATIONS

Single crystals of Cs2V4O11 were obtained in the hydrothermal CsVO3-VO (OH)(2) system and its structural chracterization was performed, Cs2V4 O11 crystallizes in the C-centered orthorhombic system: Cmm2 with a = 5.571(2) Angstrom, b = 9.639(2) Angstrom, c = 5.222(2) Angstrom and Z = 1, Structure refinements based on 402 reflections converged to R = 0 .037 and R-w = 0.044. The structure has V4O11 layers and interlayer Cs atoms. The V4O11 layer exhibits an unusual V-O network structure cons isting of VO4 tetrahedra and VO5 trigonal bipyramids in a random distr ibution. The structure is derived from that of a fictive V4O10 layer m ade up of vertex-sharing VO4 tetrahedra, That is, one-fourth of the sh ared vertices in the V4O10 layer are converted into shared edges by ad ding extra oxygens leading to the V4O11 layer; actually a vertex-shari ng VO4 dimer changes to an edge-sharing VO5 dimer, Consequently the V atom in a single crystallographic site shows two different V-O coordin ations of VO4 tetrahedra and VO5 trigonal bipyramids in a one-to-one r atio. (C) 1997 Academic Press.