Large crystal local-field effects in the dynamical structure factor of rutile TiO2

We present ab initio time-dependent density-functional calculations and nonresonant inelastic x-ray scattering measurements of the dynamical structure factor of rutile TiO{sub 2}. Our calculations are in good agreement with experiment and prove the presence of large crystal local-field effects below the Ti M edge, which yield a sharp loss peak at 14 eV whose intensity features a remarkable nonmonotonic dependence on the wave vector. These effects, which impact the excitation spectra in the oxide more dramatically than in transition metals, provide a signature of the underlying electronic structure.