Anharmonicities on Anomalous Phonon Mode in Thermal Expansion in Tungsten Oxide Crystals

点击翻译按钮获取中文摘要

The phonon-dispersion relations in the scheelite type of tungsten oxide crystals are calculated using the Lattice dynamical approach with the first-principle calculations. Raman spectra in these crsytals were measured in the broadened temperature range. The temperature dependence of linewidth of the Raman active modes were analyzed using this approach. We found that a lowest-frequency(anomalous) mode having a negative value ofγj and a clearly large phonon band gap exists in the DOS. The different behaviors in the case of temperature broadening of several modes can be attributed to this band gap.