Temperature dependent Raman spectra of the ordered and disordered phases of Ag2HgI4 and Cu2HgI4

Raman spectra of Ag2HgI4 were collected over the temperature range 8–470 °K. The ordered phase of Ag2HgI4 exhibits strong temperature dependent damping of the 85 cm−1 mode. The reduced Raman spectra of the disordered phases of both Ag2HgI4 and Cu2HgI4 are found to be temperature dependent. This unusual temperature dependence is attributed to the combined influence of anharmonicity, multiphonon processes, and the correlation time for ion hopping. An estimate of the latter was obtained from the line broadening data. Based on polarized scattering data obtained on very small crystals, symmetry assignments are made for some of the Raman bands of Ag2HgI4.