Abstract
Ab-initio calculations within density functional theory are performed to obtain a more systematic understanding of the electronic structure of iron pnictides. As a prototypical compound we study Ba0.5K0.5Fe2As2 and analyze the changes of its electronic structure when the interaction between the Fe2As2 layers and their surrounding is modified. We find strong effects on the density of states near the Fermi energy as well as the Fermi surface. The role of the electron donor atoms in iron pnictides thus cannot be understood in a rigid band picture. Instead, the bonding within the Fe2As2 layers reacts to a modified charge transfer from the donor atoms by adapting the intra-layer Fe-As hybridization and charge transfer in order to maintain an As3- valence state. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim