Mechanism of ion exchange in zirconium phosphates. 20. Refinement of the crystal structure of .alpha.-zirconium phosphate
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The preparation of high-quality zirconium phosphate, Zr(HPO4)2·H2O, crystals permitted refinement of the previously determined structure to the state where positional parameters of the exchangeable hydrogen atoms could be determined. A new unit cell, in space group P21/n rather than the standard P21/c, was chosen because of its smaller β angle. The new cell dimensions are a = 9.060 (2) Å, b = 5.297 (1) Å, c = 15.414 (3) Å, β = 101.71 (2)° and Z = 4. Intensity data were collected by the θ-2θ scan procedure using an automated four-circle diffractometer (Enraf-Nonius CAD-4). Refinement of the data (2005 independent reflections with I ≥ 3σ(I) of 3178 measured) by the full-matrix least-squares procedure with anisotropic temperature factors for all nonhydrogen atoms resulted in a final R value of 0.027. The average Zr-O bond distance is 2.064 (5) Å. Each P-OH group forms a hydrogen bond with the water molecule (O-O distances 2.807 (3) and 2.769 (3) Å). The water molecule in turn acts as donor in forming one hydrogen bond with a P-O-H oxygen. The other water hydrogen is not involved in hydrogen bonding. There are no hydrogen bonds between layers so that only van der Waals forces must hold the layers together. © 1977, American Chemical Society. All rights reserved.
author list (cited authors)
Troup, J. M., & Clearfield, A.