A LAYERED FRAMEWORK CHARACTERIZED BY 2 INDEPENDENT TUNNELS - THE SINGLE-CRYSTAL STRUCTURE OF STRONTIUM VANADIUM(III) PYROPHOSPHATE, SRV2(P2O7)2

The crystal structure of strontium vanadium (III) pyrophosphate, SrV2(P2O7)2, has been analyzed by the single crystal X-ray diffraction method. The title compound crystallizes in a triclinic (P1) unit cell, with lattice dimensions: a = 4.8006 (7)Å, b = 7.117 (1)Å, c = 7.8569 (8)Å, α = 89.92 (1)°, β = 92.38 (1)°, γ = 106.57 (1)°, V = 257.05 (6)Å3, and Z = 1. The single crystal structure refinement gives a final structure solution with R/Rw indexes on F20 of 0.021/0.030 for 100 variables and GOF = 1.38. The layered type structural framework, built up from corner-sharing VO6 octahedra and P2O7 pyrophosphate groups, possesses two types of tunnel structures of which the larger tunnels are occupied by strontium atoms. The strontium atoms are centered at the origin of the lattice and exhibit an irregular SrO10 polyhedron which can be best described as a tetra-face-capped octahedron. The structure comparison with previously reported BaTi2(P2O7)2 and NaxMoP2O7 (0.25 ≤ x ≤ 0.50) is also discussed. © 1991 Academic Press, Inc.