Modulated Structure of the Composite Crystal Ca0.83CuO2

A new vanadium (V) hydroxymonophosphate hydrate, K3(VO2)2PO4PO3OH·H2O, with a "tapelike" structure has been synthesized. This compound crystallizes in the space group P21/c with a= 5.099(1) ?, b=29.168(3) ?, c=8.115(1) ?, BETA=91.65(1)°. Its structure consists of [V2P2O11OH] ribbons built up of corner-sharing VO5 pyramids, PO4, and PO3OH tetrahedra, interleaved with K+ ions and H2O molecules. In spite of its unidimensional character, this structure forms pentagonal tunnels. Relationships with frameworks involving tetragonal tunnels are studied.