First-principles prediction of zone-center optical phonon linewidths and IR spectra of hexagonal boron nitride

Raman and infrared (IR) spectra provide rich information about materials. In this study, we employ first-principles calculations to predict the temperature-dependent linewidths of zone-center phonon modes, along with the IR dielectric function in bulk hexagonal boron nitride. We include the contributions of three-phonon, four-phonon scattering, and phonon renormalization, and our predictions show good agreement with our own experimental results as well as those in the literature. Our findings show that the temperature dependency of phonon linewidth would be strengthened by considering four-phonon scattering while weakened by further including phonon renormalization. After considering all these effects, four-phonon scattering shows a significant or even leading contribution to the linewidth over three-phonon scattering, especially at elevated temperatures.