Structure of a cobalt magnesium diphosphate: (MgxCo1-x)2P2O7

(Mg0.54Co0.46)2P2O7, Mr=254.42, monoclinic, P21/c, a=6.977 (1), b=8.330 (2), c=9.032 (9) A, β=113.74 (1)0, V=480.45 A3, Z=4, Dx=3.519 Mg m-3, λ(Mo Kanti Α)=0.71073 A, μ=47.916 cm-1, F(000)=495.2, T=293 K, R=0.029, ωR=0.034 for 1306 independent reflections with I≥3σ(I). The structure of (Mg0.54Co0.46)2P2O7 is isotypic with α-Mg2P2O7 and α-Co2P2O7. The Co and Mg atoms are distributed at random between [MO5] pyramids and [MO6] octahedra, which share their edges forming [(MgxCo1-x]2O3]∞ layers connected by layers of [P2O7] groups. A new description of the structure is proposed, in which the [MO5] pyramids are replaced by very distorted octahedra, showing its great similarity with β-V2P2O9. (orig.)