Orientational order and rotational dynamics of the amide ions in potassium amide.: II.: Quasielastic neutron scattering

The ionic molecular crystal potassium amide (KNH2) was investigated by means of quasielastic incoherent neutron scattering (QNS).:In the orientationally disordered cubic and tetragonal high-temperature phases as well as in the ordered monoclinic phase reorientational motions of the amide ions (NH2-) are resolved in a frequency range of three orders of magnitude. The QNS spectra are well explained by reorientational models for each phase. Furthermore, the results are compared to structural data and findings of other spectroscopic methods. Finally, a consistent picture of structure and dynamics of all three phases of potassium amide is obtained. (C) 1998 American Institute of Physics.