Ab Initio Description of Disordered Sr1−xKxFe2As2 Using the Coherent Potential Approximation

The electronic structure of disordered Sr1−xKxFe2As2 is studied by ab initio density functional theory. As no superstructure and/or atomic short range ordering is reported for Sr1−xKxFe2As2, the coherent potential approximation can be used to describe the effects of chemical disorder. We find clear deviations from the rigid band model characteristics. Nonmagnetic calculations show an enhancement of the density of states at the Fermi energy in the range 0.4≤x≤0.65, which coincides with the region where experiments observe an enhanced superconducting transition temperature, and antiferromagnetic calculations indicate a significant renormalization of states at Fermi energy. Analyzing the distribution of the Fe 3d states over the range 0≤x≤1 we propose an effective three band model.