STRUCTURE OF A COBALT MAGNESIUM DIPHOSPHATE - (MGXCO1-X)2P2O7

(Mg0.54Co0.46)2P2O7, M(r) = 254.42, monoclinic, P2(1)/c, a = 6.977 (1), b = 8.330 (2), c = 9.032 (9) angstrom, beta = 113.74 (1)-degrees, V = 480.45 angstrom 3, Z = 4, D(x) = 3.519 Mg m-3, lambda(Mo K-alphaBAR) = 0.71073 angstrom, mu = 47.916 cm-1, F(000) = 495.2, T = 293 K, R = 0.029, wR = 0.034 for 1306 independent reflections with I greater-than-or-equal-to 3-sigma(I). The structure of (Mg0.54CO0.46)2P2O7 is isotypic with alpha-Mg2P2O7 and alpha-Co2P2O7. The Co and Mg atoms are distributed at random between [MO5] pyramids and [MO6] octahedra, which share their edges forming [(Mg(x)Co1-x)2O3]infinity 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 beta-V2P2O9.