Synthesis and crystal structure of a new lithium nickel fluorophosphate Li2[NiF(PO4)] with an ordered mixed anionic framework

A new lithium nickel fluorophosphate Li-2[NiF(PO4)] has been synthesized. It crystallizes in the orthorhombic system with unit-cell parameters a = 10.473(3) Angstrom, b = 6.2887(8) Angstrom, c = 10.846(1) Angstrom, and space group Pnma (no. 62), Z = 8. Its structure has been determined from single-crystal X-ray diffraction data and refined to a conventional R = 0.030 (R-omega = 0.033) for 647 reflections with I > 3 sigma(I). The structure is built of infinite chains of a rutile type of NiO4F2 octahedra running along the b direction further joined together by isolated PO4 tetrahedra by sharing corners. This three-dimensional framework delimits channels parallel to the b direction where the Li+ ions lie. This compound is characterized by a rigorous O-F ordering. (C) 1999 Academic Press.