First-principles calculations and X-ray spectroscopy studies of the electronic structure of CuWO4

First-principles self-consistent band-structure calculations of copper tungstate, CuWO4, have been made using the full potential linearized augmented plane wave (FP-LAPW) method. Total and partial densities of states of the constituent atoms of CuWO4 have been derived. The results obtained reveal that the valence band of CuWO4 is dominated by contributions of the O 2p-like states, while the W 5d-like states are the main contributors into the conduction band of the tungstate. Additionally, the FP-LAPW calculations render that the W 5d- and Cu 3d-like states contribute mainly at the bottom and at the top of the valence band of CuWO4, respectively. In the present work, the X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) methods were also employed to investigate experimentally the electronic structure of copper tungstate. For the mentioned compound, the XES bands reflecting the energy distribution of mainly the W 5d-, Cu 3d- and O 2p-like states were derived and compared on a common energy scale with the X-ray photoelectron valence-band spectrum. A rather good agreement of the experimental and theoretical data concerning electronic properties of CuWO4 has been obtained in the present paper. Measurements of the energy shift of the XAS W LIII edge of CuWO4 clearly demonstrate that tungsten atoms in copper tungstate are in the formal valence state +6.