PREPARATION AND CRYSTAL-STRUCTURE OF NAVOASO4

The single phase compound NaVOAsO4 was prepared by a solid state reaction. It crystallizes in the monoclinic system, space group P2(1)/c with a = 6.650(1) angstrom, b = 8.714(1) angstrom, c = 7.221(1) angstrom, beta = 115.17(1)-degrees, Z = 4. The structure was determined from 591 reflections collected on a Nonius CAD4 automatic diffractometer with MoK-alpha radiation. The final R index and weighted Rw index are 0.032 and 0.044, respectively. The structure is built up from chains of corner-shared VO6 octahedra, parallel to the c axis, crosslinked via corner sharing by AsO4 tetrahedra. Each AsO4 group is bonded to four VO6 octahedra of which two belong to the same chain. This structure is similar to that of SbOPO4, beta-VOSO4 and beta-VOPO4. It shows the ability of this type of framework to distort in order to accommodate alkali ions.