X-RAY-POWDER STRUCTURE AND RIETVELD REFINEMENT OF GAMMA-ZIRCONIUM PHOSPHATE, ZR(PO4)(H2PO4)CENTER-DOT-2H2O

A highly crystalline sample of gamma-zirconium phosphate Zr(PO4)(H2PO4 ).2H2O has been prepared by hydrothermal methods and its structure sol ved by X-ray powder diffractometry: monoclinic, space group P2(1), a = 5.3825(2), b = 6.6337(1), c = 12.4102(4) angstrom, beta = 98.687(2)-d egrees and Z = 2. The final agreement factors are: R(wp) = 0.105, R(p) = 0.079 and R(F) = 0.041. In the structure the metal atoms and one of the phosphate groups are located nearly in a plane. The octahedral co -ordination of the metal atom is completed by four oxygen atoms of the phosphate group and two oxygen atoms of the dihydrogenphosphate group . The remaining two oxygens of the dihydrogenphosphate group bind to p rotons and project into the interlayer space. These hydroxyl groups ar e hydrogen bonded to the water molecules. The water molecules reside i n the pockets of these hydroxyl groups and are hydrogen bonded to each other to form a zigzag chain along the b axis.