Neutron powder diffraction studies of some superprotonic and mixed crystals with disordered hydrogen bonds

Neutron diffraction is well known as an effective tool for studying proton location in a crystal lattice. During the last decade, the development of high-resolution powder diffractometers has provided an alternative method to single-crystal neutron diffraction in order to obtain this detailed structural information. The powder technique is rapid and appropriate, particularly in cases where obtaining single crystals is technically difficult. In this paper, several examples of the study of crystals with disordered hydrogen bonds are presented using the High-Resolution Powder Diffractometer, at the ISIS pulsed neutron source. These include a detailed description of the hydrogen bonding and phase transition behaviour in CsHSO₄ and in Cs₃D(SeO₄)₂ and recent structural investigations on the mixed crystal K_1-x(ND₄)_xD₂PO₄.