Neutron scattering investigations of the properties of the x - T phase diagram of Rb sub 1 sub - sub x (NH sub 4) sub x I mixed crystals

The x - T phase diagram of Rb sub 1 sub - sub x (NH sub 4) sub x I is studied using samples with the ammonium concentration 0.01<x<0.77 over a wide temperature region of 15 to 300 K by neutron powder diffraction and inelastic incoherent neutron scattering. The results of powder diffraction studies show that at low temperatures a phase transition from alpha-phase to beta-phase is observed at ammonium concentrations x = 0.50 and x = 0.66. Inelastic incoherent neutron scattering detects a region of the orientional glass state at ammonium concentrations 0.29<x,0.40