The Doping Effect on the Lattices and Electronic Structure in?Superconducting Fe-based Compounds Sr1?xKxFe2As2

The lattices and density of states (DOS) for the novel superconductor Sr_1−x K _x Fe₂As₂ (x=0–1) are calculated based on the density functional theory with the scheme of the linearized augmented plane wave and the improved local orbital (APW+lo). The effects of K-doping on the lattice indicate that the K substitution induces a modification of the FeAs₄ tetrahedron into the regular one gradually. DOS calculations reveale that Fe 3d and As 4p states play a key role to the Fermi surface, the peak at x=0.5 for the total N^l(E _F) DOS at Fermi surface which would be favor of the transition of electrons, and leads to the maximal T _c in Sr_1−x K _x Fe₂As₂ system. This result was considered as a possible origin of the observed T _c behavior in the experiment of Sr_1−x K _x Fe₂As₂ system.