CRYSTALLOGRAPHY AND STRUCTURE OF ALPHA-ZIRCONIUM BIS(MONOHYDROGEN ORTHOPHOSPHATE) MONOHYDRATE

The crystal structure of α-zirconium bis(monohydrogen orthophosphate) monohydrate, Zr(HPO4)2.H2O, has been determined from integrated precession data (568 nonzero refactions). The crystals are monoclinic, space group P21/c, with cell dimensions a = 9.076 ± 0.003 Å, b = 5.298 ± 0.006 Å, c =16.22 ± 0.02 Å, and β = 111.5 ± 0.1°. The calculated density with Z = 4 is 2.76 g/cm3 compared to an observed density of 2.72 ± 0.04 g/cm3. The structurewas refined to an R factor of 8.4% byleast-squares methods. The structure is a layered one, each layer consisting of planes of zirconium atoms bridged through phosphate groups which alternate above and below the metal atomplanes. Each phosphate group bonds to three different zirconium atoms producing octahedral coordination about the zirconium atoms. The Zr-O bond distances range from 2.04 to 2.11 Å. The fourth phosphate oxygen bearsthe hydrogen and points toward an adjacent layer. The layers are arranged relative to each other in such a way as to form zeolitic-type cavities. A water molecule resides in the center of each cavity and is hydrogen bondedto phosphate groups. The relation between structure and ionexchange properties of the crystals is discussed in this and a forthcoming paper. © 1969, American Chemical Society. All rights reserved.