Phonon anharmonicity of phonon band gap effect of scheelite PbWO4 studied by Raman spectrometry and first-principles calculations

The phonon-dispersions of PbWO4 crystal are calculated using the first-principles calculations. Polarized Raman spectra in the PbWO4 were measured in the temperature range from 4 K to 280 K, and the temperature dependence of the linewidth of the Eg (193 cm−1) and Ag (906 cm−1) Raman modes was analyzed using both the first-principles calculations and lattice perturbative approach. We found that the different behaviors of these two modes in the case of temperature broadening could be attributed to the large energy band gap in the PDOS (one-phonon density of states) resulting in different anharmonic interactions. The ratio of up-conversion TDOS (temperature-weighted two-phonon density of states) to down-conversion TDOS for Eg mode (193 cm−1) is more than that for Ag (906 cm−1). Therefore, the linewidths for the Eg mode (193 cm−1) may be varied with increasing temperature by comparison with those of the Ag (906 cm−1).