First-principles APW + LO calculations and X-ray spectroscopy studies of the electronic structure of Zr6FeAl2

Electronic structure of zirconium iron aluminide, Zr6FeAl2, a very prospective hydrogen-storage intermetallic compound, has been studied from both theoretical and experimental viewpoints. In the present paper 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 have been made to elucidate total and partial densities of states of Zr6FeAl2. Due to data of the present APW + LO calculations, the Al 3s-like states dominate at the bottom of the valence band, the central portion of the valence band is dominated by the Fe 3d-like states, whilst the top of the valence band is composed mainly by contributions of the Zr 4d-, Fe 3d- and Al 3p-like states. Furthermore, the bottom of the conduction band of Zr6FeAl2 is dominated by contributions of the Zr 4d*- and Fe 3d*-like states. Regarding the occupation of the valence band of Zr6FeAl2, the APW + LO results have been confirmed experimentally by a comparison on a common energy scale of the XPS valence-band spectrum and the XES bands representing the energy distributions of the valence Zr d-, Fe d-, Al p- and Al s,d-like states in the compound under consideration. Additionally, the XPS Zr 3d, Fe 2p and Al 2p core-level binding energies have been measured for Zr6FeAl2.