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

Abstract

Employing virtual crystal approximation and super-cell methods for doping, we have performed a comparative study of the electronic structures of various doped BaFe2As2 materials by first principles simulations. Both of these methods give rise to a similar density of states and band structures in case of hole doping (K doping in Ba site) and iso-electronic P doping in As site. But in case of electron doped 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 iso-electronic Ru doping implemented by virtual crystal approximation, an extra shift of the chemical potential in electronic structure in comparison to super-cell method is observed and that shift can be used to predict the correct electronic structure within virtual crystal approximation as reflected in our calculated Fermi surfaces. But for higher Ru doping concentration, simple shifting of chemical potential does not work as the electronic structure calculated by virtual crystal approximation approach is entirely different from that of the calculated by super-cell formalism.

Electronic origin of structural transition in 122 Fe based superconductors

“…In order to dope the system theoretically, we use Virtual crystal approximation (VCA) [46,47] as well as supercell approach (specially for Ru doping at Fe site). Non-spin-polarized and spin polarised single point energy calculations are carried out for tetragonal phase with space group symmetry I4/mmm (No.…”

“…We use experimental orthorhombic (low temperature) as well as tetragonal (high temperature) lattice parameters a, b, c and z As as input of our ab-initio electronic structure calculations. In order to dope the system theoretically, we use Virtual crystal approximation (VCA) [46,47] as well as supercell approach (specially for Ru doping at Fe site). Non-spin-polarized and spin polarised single point energy calculations are carried out for tetragonal phase with space group symmetry I4/mmm (No.…”

Stoner factors of doped 122 Fe-based superconductors: First principles results

“…On the contrary, we employed VCA method to dope K, Na and P in Ba122 system. The detailed discussion about the application of VCA and super-cell methods for various doped 122 systems can be found in ref [48]. In this work, we use the VCA method, developed by Bellaiche and Vanderbilt [47] based on weighted averaging of pseudopotentials.…”

Lattice parameters and electronic bandgap of orthorhombic potassium sodium niobate K$$_{0.5}$$Na$$_{0.5}$$NbO$$_{3}$$ from density-functional theory

“…A single primitive unit cell then suffices to represent the solid solution, making the calculations extremely efficient. While the VCA is generally trusted and often describes the properties of disordered solids, including perovskites [17,18], correctly, it ignores the true local interactions that act between the real atoms, which may lead to deviations from supercell calculations [19]. The electronic properties, in particular, are very sensitive to this.…”