Hydrogen bond network of the layered phosphates γ-Zr(H2PO4)(PO4)⋅2H2O and γ-Hf(H2PO4)(PO4)⋅2H2O determined by neutron powder diffraction
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M.A. Salvadó
Abstract
The hydrogen atom positions of the layered phosphates Zr(PO4)(H2PO4)⋅2H2O (γ-ZrP) and Hf(PO4)(H2PO4)⋅2H2O (γ-HfP) have been determined from neutron powder diffraction data and the complete crystal structures have been refined by the Rietveld method. The compounds crystallize in the monoclinic space group P21. The final agreement factors are: Rwp = 1.47, Rexp = 0.91 for γ-ZrP and Rwp = 1.73, Rexp = 1.43 for γ-HfP. The two compounds are isostructural and posses a dense hydrogen-bonding network. They are formed by layers consisting of two planes of metallic atoms joined by phosphate and dihydrogenphosphate groups. The interlayer space form channels where each water molecule accepts and donates an hydrogen bond to another water molecule forming a zig-zag chain. Additionally each water molecule acts as acceptor and donor in two hydrogen bonds with oxygen atoms of the same layer. Consecutive layers are, in this way, indirectly held together by hydrogen bonds through the water molecules.
© 2001 Oldenbourg Wissenschaftsverlag GmbH
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Articles in the same Issue
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- Determination, prediction, and understanding of structures, using the energy landscapes of chemical systems - Part I
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- Elastic and thermoelastic properties of selected organic crystals: acenaphthene, trans-azobenzene, benzophenone, tolane, trans-stilbene, dibenzyl, diphenyl sulfone, 2,2´-biphenol, urea, melamine, hexogen, succinimide, pentaerythritol, urotropine, malonic acid, dimethyl malonic acid, maleic acid, hippuric acid, aluminium acetylacetonate, iron acetylacetonate, and tetraphenyl silicon
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