BA3V2O4F8-[V4(O,F)20]8- TETRAMERIC GROUPS OF OCTAHEDRA INSERTED IN A TRIDIMENSIONAL NETWORK OF (FBA4) TETRAHEDRA

Ba3V2O4F8 is prepared by hydrothermal synthesis. The crystal structure is established from single crystal X-ray diffraction data: Space group Pnnm, Z = 4, a = 9.945(4) angstrom, b = 10.277(1) angstrom and c = 9.673(1) angstrom (R = 0.0331, R(w) = 0.0315 for 892 independent reflections and 86 parameters). The structure is related to that of Ba3Al2F12 and is described in terms of isolated [V4(O, F)20]8- tetrameric groups of octahedra inserted in a tridimensional network of (FBa4) tetrahedra. Location of oxygen and fluorine atoms is discussed with the help of bond valence calculations.