Full ab initio calculation of second‐order Raman spectra of semiconductors

We present the first full ab initio calculation of second‐order Raman spectra in semiconductors based on density functional perturbation theory. The method is applied to the Γ spectra of the elemental semiconductors diamond, silicon, and germanium and reproduces the experimental data excellently. Using first‐principles phonons, we also calculated the corresponding overtone densities of states and Γ Raman spectra employing phenomenological polarizability coefficients. Finally, we analyze the results of the different approaches pointing out the relevance of a full first‐principles derivation.