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 mu(B) magnetic moment on Fe atoms; and the J(1) and J(2) 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.