Electronic Structure of KFe₂Se₂ from First-Principles Calculations

Electronic structures and magnetic properties for iron-selenide KFe₂Se₂ are studied by first−principles calculations. The ground state is collinear antiferromagnetic with calculated 2.26 μ_B magnetic moment on Fe atoms; and the J₁ and J₂ coupling strengths are calculated to be 0.038 eV and 0.029 eV. The states around E_F are dominated by the Fe 3d orbitals which hybridize noticeably to the Se 4p orbitals. While the band structure of KFe₂Se₂ is similar to a heavily electron−doped BaFe₂As₂ or FeSe system, the Fermi surface of KFe₂Se₂ is much closer to the FeSe system since the electron sheets around M are symmetric with respect to x–y exchange. These features, as well as the absence of Fermi surface nesting, suggest that the parent KFe₂Se₂ could be regarded as an electron doped FeSe system with possible local moment magnetism.