Electronic structure of AFe 2P 2, A = Ca,Sr,Ba

Abstract

The compounds CaFe 2P 2, SrFe 2P 2 and BaFe 2P 2 crystallize in the ThCr 2Si 2 structure which is a ternary variant of the BaAl 4 structure. In order to investigate the bonding properties, band-structure calculations using the full-potential linearized augmented plane wave (FLAPW) method have been performed. For the three compounds densities of states (DOS), local partial DOS and electron densities have been calculated. Compared to CaNi 2P 2 with a PP distance of 2.30 Å, a value very close to that for a PP single bond, this distance is 2.71 Å for CaFe 2P 2. While in the latter compound one still observes pronounced PP(ss and pp) σ-bonds, this is not the case, apart from very weak pp interactions, for SrFe 2P 2 and BaFe 2P 2 (PP distances: 3.43 Å and 3.84 Å, respectively). Despite their different c/ a ratios the Sr and Ba compounds show fairly similar bonding properties, in particular as far as the FeFe and FeP interactions are concerned. In BaFe 2P 2, however, non-negligible interactions of the semicore [Ba(5p)] states with the P(3s) states are found.