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Neutron-scattering study of the dynamics of ammonium in different phases of halides of K |
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| Authors: | I. Natkaniec L. S. Smirnov L. A. Shuvalov |
| Affiliation: | (1) Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, Krakow, 31-342, Poland;(2) Joint Institute for Nuclear Research, ul. Zholio-Kyuri 6, Dubna, Moscow oblast, 141980, Russia;(3) Institute of Theoretical and Experimental Physics, State Science Center of the Russian Federation, Bol’shaya Cheremushkinskaya ul. 25, Moscow, 117218, Russia;(4) Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii pr. 59, Moscow, 119333, Russia |
| Abstract: | The effect of temperature and the concentration of ammonium on the lattice parameters and the amplitude-weighted phonon density of states in mixed salts of ammonium potassium halides is studied by neutron powder diffraction and incoherent inelastic neutron scattering. It is found that at 10 K incoherent inelastic neutron scattering spectra show four different excitation modes of ammonium: two resonant excitations below the cutoff energy of the phonon density of states of potassium halide and two localized excitations above the cutoff energy. The high-energy localized modes correspond to translational and librational vibrations of NH4 ions in the crystal lattice. These modes are typical of ordered phases of ammonium halides. |
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