INELASTIC X-RAY-SCATTERING FROM TIC AND TI SINGLE-CRYSTALS

Inelastic x-ray scattering spectra were measured with incident x rays having an energy near 8 keV for a range of momentum transfers q extend ing from 0.70 to 2.0 Angstrom(-1). We find spectral features correspon ding to valence electron excitations, as well as Raman scattering corr esponding to excitation from the 3p core states to the 3d valence stat es of Ti. The spectral features corresponding to valence electron exci tations lie in the regime conventionally interpreted as a bulk plasmon together with intraband and interband transitions. We compare our dat a for TiC at q=1.05 Angstrom(-1) with calculations for the dynamical d ielectric constant epsilon(q,omega) based on local-density theory. The agreement between the data and calculations permits us to interpret c ertain features in the spectra as arising from band transitions out of the strongly hybridized C 2p-Ti 3d band. The energy loss position of the Raman scattering peak is independent of momentum transfer for both TiC and Ti and lies at 48 eV for Ti. This value is above the highest- lying x-ray ultraviolet absorption resonance for atomic Ti at 43.5 eV. This shift in the data to higher energy transfer is consistent with e lectron energy loss spectra and photoemission results reported in the literature and indicates that important physical processes are not enc ompassed within existing theoretical approaches to x-ray Raman scatter ing.