First-principles Predictions of Temperature-dependent Raman and Optical Responses

High temperature applications require theoretical understanding on how optical properties would change with rising temperatures. We report here our first-principles study of infrared-active phonon modes of MgO and CeO₂ as a function of temperature. Their temperature-dependent optical properties like refractive index, extinction coefficients and further the reflectance are calculated and compared to available experiments. By considering thermal expansion, four-phonon scattering and phonon renormalization effect, we show a unified methodology to determine the optical properties of ceramic materials when they work under high temperature.