| Autor: |
Prask, H. J., Choi, C. S., Chesser, N. J., Rosasco, G. J. |
| Předmět: |
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| Zdroj: |
Journal of Chemical Physics; 4/15/1988, Vol. 88 Issue 8, p5106, 17p |
| Abstrakt: |
Single-crystal and powder neutron diffraction, coherent neutron inelastic scattering, and Raman spectroscopy have been used to study the low temperature structure and dynamics of ammonium perchlorate. No evidence for a phase transition is found. Based on analysis of thermal motion amplitudes and inelastic neutron-scattering data for ND4ClO4 a Raman-active B3g symmetry zone-center mode at 45 cm-1 is identified as a libration. Another Raman-active mode, B1g symmetry at 33 cm-1, and a previously unobserved Au symmetry mode at 12 cm-1, are inferred to have significant librational character at q=0. Comparison of these results with earlier incoherent neutron scattering results suggests that, because of the low activation energy of ammonium ions, classical jump reorientations strongly influence ammonium-ion sublattice dynamics even to temperatures as low as 20 K. Partial dispersion curves are also presented. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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