Lattice dynamics of RuO 2 : Theory and experiment

Although ${\mathrm{RuO}}_{2}$ has been studied as a prototype catalyst for $\mathrm{CO}$ oxidation, no careful study of the lattice dynamics for this material has been presented so far. Using modern ab initio methods we obtain the phonon dispersion and the generalized density of states (GDOS). Inelastic neutron scattering experiments allow for an experimental determination of the GDOS. In contrast to what is known from structural studies, we find that the local density approximation gives a much better description of the phonon spectrum than the generalized gradient corrected form. This is also consistent with Raman measurements. Our findings have important consequences for all quantities depending on the phononic part of the free energy.