Calculating Phonons within the FLAPW Method using Density Functional Perturbation Theory (DFPT)*

Computing phonons using density functional perturbation theory (DFPT) within all-electron DFT methods is a real challenge due to the displacement of muffin-tin spheres and sphere-centered basis functions. In this talk, we present our implementation of the DFPT approach within the FLAPW method, encoded in the FLEUR code (www.flapw.de). We show first results, which we compare to the phonon dispersion, calculated with the finite displacement method. We find a very good agreement and discuss what conceptual details are important to ensure the numerical accuracy required for the determination of the phonon dispersion.