Lattice Vibrations in Ammonium Chloride in the Low-Temperature Ordered Phase
- 15 September 1972
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 57 (6) , 2291-2298
- https://doi.org/10.1063/1.1678583
Abstract
A rigid‐molecule model is used to analyze the lattice vibrations in ammonium chloride in the ordered phase (III). The ammonium and chlorine are treated as rigid ions with a partial charge, and short‐range forces out to the third nearest neighbor are considered. The model is shown to give a good fit of the neutron dispersion curve data on ND4Cl at 85°K. Lattice frequency spectra are computed and decomposed into components associated with chlorine vibrations and ammonium translations and librations. Comparison with a recent shell‐model calculation shows that the numerical results are quite similar. The present results are also used to discuss the lattice heat capacity, mean square displacements, and incoherent neutron scattering.Keywords
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