The crystal and magnetic structures of BiMnO 3 were studied at high pressures up to 10 GPa by means of neutron diffraction in the temperature range 2-300 K. Three structural modifications, two monoclinic and one orthorhombic were found to exist in the pressure range studied and their structural parameters were determined. A suppression of the initial ferromagnetic state and formation of a new antiferromagnetic state with a propagation vector ͑1/2 1/2 1/2͒ was observed at P ϳ 1 GPa, accompanied with the monoclinic-monoclinic structural transformation. Possible mechanisms of the pressure-induced magnetic transition and origin of magnetoelectric phenomena in BiMnO 3 are discussed.

High-resolution neutron powder diffraction data were used to determine the crystal structure of the superionic conductor CsDSO4 at 300K (lowconductivity phase) and at 448 K (superionic phase). A full structural analysis was performed, using the Rietveld method, to obtain previously unknown atomic positions, site occupancies and temperature factors for the light atoms. The mechanism of deuterium diffusion is discussed. At 300 K: monoclinic, P2~/c, a = 7.78013 (9), b = 8.13916 (2), c = 7.72187 (9) A, fl = 110.8720 (4) °, Rwp = 4.19% for 7331 profile points (844 reflections). At 448 K: tetragonal, 141/amd, a = 5-74147 (9), c --14-31508 (26) A, Rwp = 2"21% for 8289 profile points (194 reflections).

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The diffusion of protons in the superionic phase of CsHSO4 was investigated by quasielastic neutron scattering (QNS) on the IRIS spectrometer at the pulsed spallation neutron source ISIS, Rutherford Appleton Laboratory, UK. Two processes with different characteristic times could be distinguished: long-range translational diffusion with a diffusion coefficient D=(1.00-1.17)*10-7 cm2 s-1 (for a temperature range from 423 to 448 K) and jump rotation of HSO4 groups between two possible orientations, the corresponding nonequivalent proton sites being 2.3 AA apart.

Lattice dynamics of the ordered y-ZrH phase was studied by inelastic n e u b scattering (ms). It was found the hydrogen optical peak in the mrs specr" had three " a at mergy kansfess of 141.5, 148.7 and 156.3 meV. The peak was accuatdy described using the Bom-von Kanoan model. Anhamonicily of hydrogen vibrations was evident in the high-energy range of Le s p e c " from a strong sharp peak at E = 269.7meV and broader features below the bands of free-multiphonon scattering. These anhamonic phenomena were amibuted to the bund multiphonon Sates (biphonon, hiphonon, tetraphonon and heir combinations), and the values of the binding energies of biphonons and triphonons were obtained from the experimental data.