Observation of coupled amplitude modes in the Raman spectrum of incommensurate Na2CO3
- 30 June 1981
- journal article
- Published by IOP Publishing in Journal of Physics C: Solid State Physics
- Vol. 14 (18) , L509-L514
- https://doi.org/10.1088/0022-3719/14/18/007
Abstract
Temperature-dependent phonons have been observed in the Raman spectrum of incommensurate psi -Na2CO3. Two modes are identified as q approximately=0 librational modes of the CO32- groups, which soften at the alpha - beta transition at Tc1=763K. At Tc2=633K a modulation of the structure sets in which is believed to be due to a softening of a librational mode at the incommensurate wavevector q*. Two additional lines that the authors observe in the gamma -phase are assigned to coupled amplitude modes that arise from the coupling of acoustic and librational branches at q=q*.Keywords
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