STRUCTURE AND DYNAMICS OF DIFFERENT PHASES OF THE SUPERPROTONIC CONDUCTOR CSHSO4

Caesium hydrogen sulphate (CsHSO4) shows a rich variety of phases in t he pressure-temperature phase diagram. The crystal structures of these phases have been studied by the neutron-diffraction method. The latti ce dynamics of several crystallographic phases have also been studied by the inelastic neutron scattering, It is shown that anharmonicity pl ays an important role in the dynamic properties of phases occurring at ambient pressure, High pressure reduces the effects of anharmonicity and the crystal phase which appears at a pressure of 1.7 GPa exhibits harmonic behaviour.