Inelastic neutron scattering study of Cs1-x(NH4)(x)HSO4 mixed crystals

Inelastic neutron scattering and X-ray diffraction study were performed on Cs1-x(NH4)(x)HSO4 mixed crystals for x = 0.05 and 0.1. From the experimental data it follows that small concentrations of NH4 ions stabilize phase II of pure CsHSO4 while this pure crystal undergoes a phase transition into this phase only at elevated temperature. Comparative analysis of available data on optical spectroscopy of Cs1-xPbxHSO4 crystals reveals that small concentrations of Rb ions produce the same effect as NH4 ions. These observations allowed to make some conclusions about pressure-temperature-phase diagram of pure CsHSO4.