Temperature Dependence of Raman Scattering and Partial Disorder in AgI Crystals

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Abstract
A detailed study is made of vibrational dynamics in silver iodide by the temperature dependence of Raman scattering from liquid helium temperature up to melting. A complete set of data like temperature dependence of intensity of all features, of the degree of polarization of the spectra, of peak position and halfwidth clarifies the complex nature of dynamics of β‐AgI. It is shown that the anomalous features of Raman spectra are very likely due to the one‐phonon density of states connected with the onset of partial disorder in the β‐phase. In α‐phase an anomalous decrease of Raman cross section is found with increasing temperature: this effect is connected with the possibility of a continuous partial order‐disorder transition at ≈︁ 430 °C.