NaxMoP2O7, a mixed valence molybdenum diphosphate with a tunnel structure

The crystal structure of Na0.3MoP2O7 has been solved by threedimensional single crystal X-ray analysis. The refinement in the cell of symmetry PI with a = 4.8813(6) A, b = 7.0110(5) A, c = 8.2563(4) A, α = 91.400(5) Α, β = 92.466(8)°, y = 106.551(9)°, Ζ = 2 has led to R = 0.030 and Rw = 0.031 for 3327 reflections with I > 3σ(/). The framework of the structure, built up from corner-sharing Mo06 octahedra and diphosphate groups, delimits large octogonal tunnels where the Na ions are located. This structure is closely related to that of NaMoP207 which differs only by the stacking of similar layers.