Anharmonic line shift and linewidth of the Raman mode in covalent semiconductors

Combining density-functional perturbation theory with the frozen-phonon approach, the anharmonic shift of the Raman frequency of the covalent semiconductors diamond and silicon are determined ab initio. The temperature dependence of the Raman frequency and the contribution of zero-point motion are calculated as well as the Raman linewidth. Corresponding results for germanium have been obtained with the assumption that the quartic anharmonic force constants may be approximated by those of silicon.