AMMONIUM DYNAMICS IN RB1-X(NH4)(X)SCN MIXED-CRYSTALS AT 10 K

The neutron scattering studies of the ammonium dynamics in the Rb1-x(N H4)(x)SCN mixed crystals carried out at 10 K, in wide range of ammoniu m concentrations (0 < x < 1), are compared with the results obtained F or K1-x(NH4)(x)SCN. The generalized density of phonon states obtained for Rb1-x(NH4)(x)SCN is similar to K1-x(NH4)(x)SCN except for the abse nce of the low-energy resonance ammonium mode in the disordered orthor hombic phase. Results of these investigations shaw the influence of in ner strains, which appear in the K1-x(NH4)(x)SCN solid solution due to the ionic size difference between K+ and NH4+ (1.33 and 1.47 Angstrom , respectively), on the dynamics of ammonium ion.