In one set of measurements

PHYSICS · Multi-part · Fermi University Physics · Condensed Matter, Materials & Soft Matter · Dielectric and optical properties of solids · Dielectric and optical properties of solids

Solid State Physics, Ch Dielectric response, local fields and ferroelectricity

Problem

In one set of measurements, different from the LiF values quoted in the chapter text, LiF has εs=9.27\varepsilon_s=9.27 and ε∞=1.96\varepsilon_\infty=1.96, and its zone-centre longitudinal optical phonon has been measured by infrared reflectivity to be ωLO=19.8 THz\omega_{LO}=19.8\,\mathrm{THz} (81.9 meV). ((a)) Use the Lyddane-Sachs-Teller relation to predict ωTO\omega_{TO}, in THz and in meV. ((b)) The transverse optical mode measured independently by infrared absorption is ωTO=9.1 THz\omega_{TO}=9.1\,\mathrm{THz} (37.6 meV). State the percentage difference from the prediction.

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