Neutron powder diffraction study of α-Ti(HPO₄)₂.H₂O and α-Hf(HPO₄)₂.H₂O; H-atom positions

The complete crystal structures, including H-atom positions, of α-Ti(HPO₄)₂.H₂O (α-TiP) and α-Hf(HPO₄)₂.H₂O (αHfP) were determined by Rietveld refinement and Fourier synthesis, using constant-wavelength neutron diffraction data. This work is one of few recent examples of the determination of H atoms using neutron powder diffraction with an intense source. The orientation of water molecules in the cavities of α-TiP is similar to that previously found for α-ZrP. For α-HfP, although the hydrogen-bonding scheme is identical, the orientation of water molecules in similar cavities was found to be different.

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