The electronic structure of disordered ${\mathrm{Sr}}_{1-x}{\mathrm{K}}_x{\mathrm{Fe}}_2{\mathrm{As}}_2$ is studied by ab initio density functional theory. As no superstructure and/or atomic short range ordering is reported for ${\mathrm{Sr}}_{1-x}{\mathrm{K}}_x{\mathrm{Fe}}_2{\mathrm{As}}_2$, 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 $0.4\le x\le 0.65$, 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 $0\le x\le 1$ we propose an effective three band model.

• Received 13 March 2010

DOI:https://doi.org/10.1103/PhysRevLett.104.177006