The actual structure of K6(VO)2(V2O3)2(PO4)4(P2O7):: Ordered distribution of P2O7 groups and charge ordering of vanadium

The actual structure of the vanadium phosphate K-6(VO)(2)(V2O3)(2)(PO4)(4)(P2O7) has been determined, using a much larger single crystal than previously used for the isostructural Rb-phase. The actual supercell is four times larger than the corresponding orthorhombic subcell with a = 26.777 angstrom, b = 28.480 angstrom, c = 6.972 angstrom, alpha = beta = gamma = 90 degrees. The structure resolution, performed in the triclinic space group C-1, shows that the P2O7 groups alone are responsible for the superstructure, all the other atoms keeping the atomic positions of the orthorhombic subcell. This structural study shows a perfect ordering of the P2O7 groups in the actual structure, in contrast to the results obtained from the subcell. Concomitantly, the V4+ and V5+ are found to be ordered in the form of [110] stripes. (c) 2005 Elsevier Inc. All rights reserved.