Local Field Effects in the Electron Energy Loss Spectra of Rutile [Formula presented]

We present an ab initio calculation of the electron energy loss spectrum of rutile [Formula presented] in the energy range of 0 to 60 eV, focusing our interest on the excitation from the titanium [Formula presented] semicore levels. The results are compared to our measurements. Local field effects turn out to be crucial at those energies, and their inclusion in the calculation yields excellent agreement between theory and experiment. We show how in rutile these effects induce an anisotropy in the otherwise isotropic transitions from quasispherical [Formula presented] semicore states to [Formula presented] states of almost cubic symmetry.