Electronic structures of doped BaFe2As2 materials: virtual crystal approximation versus super-cell approach

Using virtual crystal approximation and super-cell methods for doping, a detailed comparative study of electronic structures of various doped BaFe2As2 materials by first principles simulations is presented. Electronic structures remain unaltered for both the methods in case of passive site doping but in case of active site doping, the electronic structure for virtual crystal approximation method differ from that of the super-cell method specially in the higher doping concentrations. For example, both of these methods give rise to a similar density of states and band structures in case of hole doping (replacing K in place of Ba) and isovalent P doping on As site. But in case of electron doped (Co in place of Fe) systems with higher doping concentration, electronic structures calculated using virtual crystal approximation approach deviates from that of the super-cell method. On the other hand, in case of low isovalent Ru doping at the Fe site implemented by virtual crystal approximation, one acquires an extra shift in the chemical potential in comparison to that for the super-cell method. This shift may be utilized to predict the correct electronic structure as well as the calculated Fermi surfaces within virtual crystal approximation. But for higher Ru (that has different electronic configuration than Fe) doping concentration, simple shifting of chemical potential fails, the calculated electronic structure via virtual crystal approximation approach is very different from that by the super-cell formalism.