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Experimental Raman scattering investigation of phonon anharmonicity effects in Li2S

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Published in Journal of Physics. Condensed Matter. 1998, vol. 10, no. 9, p. 2155-2169
Abstract Experiments in which the Raman linewidth was measured as a function of temperature (7–1183 K) and pressure (0–400 bar) were performed on the (111) and (100) planes of single crystals of the cubic anti-fluorite Li2S. The temperature dependence of the lattice constant was determined by x-ray diffraction (11–295 K). From these results and published Brillouin scattering data for this host, the volume thermal expansion coefficient as a function of temperature was obtained as well as the isothermal compressibility and the isothermal Raman mode Grüneisen parameter. Using the thermodynamic approach within the quasi-harmonic approximation, we show that below 400 K the volume effects describe well the temperature dependence of the Raman linewidth whereas above this temperature there are direct anharmonic effects appearing. Above approximately 850 K new Raman lines appear that are A1 and E polarized.
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Research group Groupe Bill
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BERTHEVILLE, Bernard, BILL, Hans, HAGEMANN, Hans-Rudolf. Experimental Raman scattering investigation of phonon anharmonicity effects in Li2S. In: Journal of Physics. Condensed Matter, 1998, vol. 10, n° 9, p. 2155-2169. https://archive-ouverte.unige.ch/unige:2751

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Deposited on : 2009-09-21

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