STRUCTURE OF NA3.12FE2.44(P2O7)(2)

A sodium-iron (II) diphosphate, Na3.12Fe2.44(P2O7)(2), has been synthe sized by solid state reaction and characterized by single-cristal X-ra y diffraction. The compound crystallizes in the triclinic space group P ($) over bar 1 with a = 6.424(2) Angstrom. b = 9.440(1) Angstrom, c = 10.981(2) Angstrom, alpha = 64.77(1)degrees, beta = 86.21(2)degrees, gamma = 73.13(2)degrees, V = 575(3) Angstrom(3), and Z = 2. The struc ture presents two types of centrosymmetrical units : each crown Fe2P4O 22 and Fe2P4O20 consists of two FeO6 octahedra and two P2O7 groups, ea ch in a nearly eclipsed conformation. These crowns are connected by co rner-sharing to form a three-dimensional framework with different inte rconnected tunnels running along [100]. The tunnels contain Na and Fe atoms, some of them in partially or mixed occupied sites.