Electronic structure of monoclinic α-KY(WO4)2 tungstate as determined from first-principles FP-LAPW calculations and X-ray spectroscopy studies

Total and partial densities of states of the constituent atoms of potassium yttrium double tungstate, KY(WO4)2 (KYW), have been calculated using the first-principles self-consistent full potential linearized augmented plane wave (FP-LAPW) method. The results derived reveal that the O 2p-like states are the dominant contributors into the valence band of KYW, while the conduction band of the compound is dominated by contributions of the W 5d-like states. The FP-LAPW calculations render that KYW is an indirect-gap material with the band-gap value of 3.645 eV. The X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) methods were also used in the present work to study experimentally electronic properties of potassium yttrium double tungstate. For the above compound, the XES bands reflecting the energy distribution of the valence W d-, O p- and K p-like states were derived and compared on a common energy scale with the X-ray photoelectron valence-band spectrum. Measurements of the energy shift of the XAS W LIII edge of KYW reveal that tungsten atoms are in the formal valence state 6+. A rather good agreement of the experimental XES and theoretical FP-LAPW data concerning electronic properties of KYW has been obtained in the present paper.