Theoretical study of the X-ray absorption spectra of Mg 2FeH 6

Abstract

The energy bands, total density of states (DOS) and partial wave analysis of the DOS around the iron, magnesium and hydrogen sites of non-conducting Mg 2FeH 6 have been studied up to 20 eV above the energy gap by means of the augmented plane wave method. From these theoretical results we predict in the constant matrix element approximation the shapes of the Fe L and Mg K absorption spectra which correspond to transitions to iron 3d and magnesium 3p empty states respectively. We conclude from our results that the study of X-ray absorption spectra and particularly that of the transition metal L absorption edge, presents features which are the signature of the K 2PtCl 6-type crystal structure and can thus help in identifying the hydrogen site occupancy in the cubic phase of the isoelectronic and isostructural compounds Mg 2FeH 6, Mg 2CoH 5 and Mg 2NiH 4.