Large crystal local-field effects in the dynamical structure factor of   rutile TiO2
  We present ab initio time-dependent-density-functional calculations and non-resonant inelastic x-ray scattering measurements of the dynamical structure factor of rutile TiO2. 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 non-monotonic 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. 
I.G.Gurtubay, Wei Ku, J.M.Pitarke, A.G.Eguiluz, B.C.Larson,   J.Tischler, and P.Zschack