Electronic structure of oxygen-free 38K superconductor Ba1-xKxFe2As2 in   comparison with BaFe2As2 from first principles
  Based on first-principles FLAPW-GGA calculation, we have investigated electronic structure of newly discovered oxygen-free 38K superconductor Ba1-xKxFe2As2 in comparison with parent phase - tetragonal ternary iron arsenide BaFe2As2. The density of states, magnetic properties, near-Fermi bands compositions, together with Sommerfeld coefficients and molar Pauli paramagnetic susceptibility are evaluated. The results allow us to classify these systems as quasi-two-dimensional ionic metals, where the conduction is strongly anisotropic, only happening on the (Fe-As) layers. According to our calculations, at the hole doping of BaFe2As2 the density of states at the Fermi level grows, and this can be a possible factor of occurrence of superconductivity for Ba1-xKxFe2As2. On the other hand, Ba1-xKxFe2As2 lays at the border of magnetic instability and the pairing interactions might involve magnetic or orbital fluctuations. 
I.R. Shein, A.L. Ivanovskii