NEUTRON SPECTROSCOPY OF THE K1-X(NH4)(X)I SOLID-SOLUTION

The concentration and temperature dependences of the generalized densi ty of phonon states of the disordered cubic alpha-phase (the NaCl-type lattice) and the ordered hexagonal gamma-phase (the CsCl-type lattice ) of the K1-x(NH4)(x)I solid solution have been studied by the method of inelastic incoherent neutron scattering. The concentration dependen ces of the energies of the lattice modes of an ammonium ion are obtain ed at 10 K. In the disordered alpha-phase, they consist of two resonan ce and two local modes, whereas in the ordered gamma-phase, they consi st of only two local modes. The most low-energy resonance mode of the alpha-phase has been observed for the first time.