Electronic structure of Zr4Fe2O: Ab initio APW+LO calculations and X-ray spectroscopy studies

Abstract First-principles band-structure augmented plane wave +local orbitals (APW+LO) calculations as incorporated in the WIEN2k code as well as X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) measurements are performed to elucidate the electronic structure of Zr 4 Fe 2 O oxide, a very prospective hydrogen-storage material. Total and partial densities of states for Zr 4 Fe 2 O are derived from the APW+LO calculations. The XPS valence-band spectrum as well as the XES Zr Lβ 2,15 , Fe L α and O K α bands are measured for Zr 4 Fe 2 O 0.6 oxide. Our APW+LO calculations show that the O 2p-like states make the major contributions at the bottom of the valence band, whilst the Fe 3d- and Zr 4d-like states are the dominant contributors at the top of the valence band and at the bottom of the conduction band of Zr 4 Fe 2 O. Peculiarities of the occupation of the valence band of Zr 4 Fe 2 O predicted by the APW+LO calculations are confirmed experimentally by comparison, on the common energy scale, of the XPS valence-band spectrum and the XES bands representing the energy distributions of the Zr 4d-, Fe 3d- and O 2p-like states in the compound under consideration. In addition, the XPS Zr 3d, Fe 2p and O 1s core-level binding energies are derived for Zr 4 Fe 2 O 0.6 oxide.