Electronic structure of polycrystalline cadmium dichloride studied by X-ray spectroscopies and ab initio calculations

The electronic structure of cadmium dichloride has been studied by X-ray absorption near edge structure (XANES) and, for the first time, by resonant inelastic X-ray scattering (RIXS) at the Cl K edge. Good agreement was obtained between the non-resonant X-ray emission (XES) along with XANES experimental spectra and the calculated Cl 3p local partial density of states (DOS). The calculations were performed using the full-potential linearized-augmented-plane-wave with the local orbitals (FP-(L) APW_lo) method utilized in the WIEN2k code. It was shown that the position of the RIXS band in CdCl2 follows a linear dispersion according to the Raman-Stokes law if the excitation energy is tuned below the absorption threshold. The situation changes for core excitation above the photoabsorption threshold where the dispersion relation is split into two branches. The position of the resonant contribution does not depend on the excitation energy, while the excitonic sideband follows the Raman-Stoke law. Combined XANES and RIXS measurements compared to calculated band structure allowed us to determine the direct band gap of CdCl2 to be at 5.7 +/- 0.05 eV. (C) 2012 Elsevier B.V. All rights reserved.