Ab initio x-ray absorption near-edge structure study of Ti K-edge in rutile

Abstract

This work reports a theoretical x-ray absorption near-edge structure (XANES) spectroscopy study at the TiK-edge in TiO2 rutile. We present detailed ab initio computations of the Ti K-edge XANES spectrumperformed within the multiple-scattering framework. An extensive discussion is presentedconcerning the size of the cluster needed to reproduce the experimental spectrum,especially regarding the split main absorption line. In addition, the role of theexchange and correlation potential (ECP) in reproducing all the experimentalXANES features is discussed. The best agreement between experimental data andcomputations is obtained by using real ECP potentials, i.e. the energy-dependentDirac–Hara exchange potential, or by using only the real part of the energy-dependentHedin–Lundqvist complex potential, together with an additional imaginary constant toaccount for the core-hole lifetime and the experimental resolution. The additionof the imaginary part of the HL potential worsens the agreement between theexperimental and calculated spectra, indicating the failure of the complex part of theHedin–Lundqvist ECP in accounting for the electron damping in these systems.