First-Principle Electronic Structure Calculation of BaFe2−xCoxAs2(x = 0, 1, 2) Superconductor

The equilibrium crystal structure and electronic structure of BaFe2−xCoxAs2 (x = 0.0, 1.0, 2.0) superconductor have been investigated by using the pseudopotential Quantum Espresso code based on the ab initio density functional theory in the generalized gradient approximation. The equilibrium crystal structure for x = 1.0 has been determined by considering five different Fe/Co configurations. This study shows that the spin calculation is essential to obtain the experimental values at x = 0.0. The total and partial density of states, band structure, and Fermi surfaces of the three compounds has been calculated. Density of states calculation indicates the important role of Fe/Co3d and As4p orbitals in the valance states, and a downward shift of the states to the lower energies. Band structures show rigid band shift by Co doping resulting in removing of two crossing Fermi level hole-like bands. In parallel, topology of the Fermi surfaces considerably changes by Co doping, resulting in the disappearing of the hole carriers regions and the extension of the electron Fermi surfaces volume. This study might lead us to better understanding of the role of Co doping element and its underlying physics in this system.